Word order: head-final and left-branching

The modern theory of constituent order ("word order"), usually attributed to Joseph Harold Greenberg, identifies several kinds of phrases. Each one has a head and possibly a modifier. The head of a phrase either precedes its modifier (head-initial) or follows it (head-final). Some of these phrase types, with the head marked in boldface, are:

• genitive phrase, i.e., noun modified by another noun ("the cover of the book", "the book's cover");
• noun governed by an adposition ("on the table", "underneath the table");
• comparison ("[X is] bigger than Y", i.e., "compared to Y, X is big").
• noun modified by an adjective ("black cat").

Some languages are inconsistent in constituent order, having a mixture of head-initial phrase types and head-final phrase types. Looking at the preceding list, English for example is mostly head-initial, but nouns follow the adjectives which modify them. Moreover, genitive phrases can be either head-initial or head-final in English. By contrast, the Japanese language is consistently head-final:

• genitive phrase:

• noun governed by an adposition:

• comparison:

• noun modified by an adjective:

Head-finality in Japanese sentence structure carries over to the building of sentences using other sentences. In sentences that have other sentences as constituents, the subordinated sentences (relative clauses, for example), always precede what they refer to, since they are modifiers and what they modify has the syntactic status of phrasal head. Translating the phrase "the man who was walking down the street" into Japanese word order would be "street down walking was man".^{[lower-alpha 2]}

Head-finality prevails also when sentences are coordinated instead of subordinated. In the world's languages, it is common to avoid repetition between coordinated clauses by optionally deleting a constituent common to the two parts, as in "Bob bought his mother some flowers and his father a tie", where the second bought is omitted. In Japanese, such "gapping" must proceed in the reverse order: "Bob mother for some flowers and father for tie bought". The reason for this is that in Japanese, sentences (other than occasional inverted sentences or sentences containing afterthoughts) always end in a verb (or other predicative words like adjectival verbs, adjectival nouns, auxiliary verbs)—the only exceptions being a few sentence-ending particles such as ka, ne, and yo. The particle ka turns a statement into a question, while the others express the speaker's attitude towards the statement.

Word class system

Japanese has five major lexical word classes:

• nouns
• verbal nouns (correspond to English gerunds like 'studying', 'jumping', which denote activities)
• nominal adjectives (names vary, also called na-adjectives or "adjectival nouns")
• verbs
• adjectives (so-called i-adjectives)

More broadly, there are two classes: uninflectable (nouns, including verbal nouns and nominal adjectives) and inflectable (verbs, with adjectives as defective verbs). To be precise, a verbal noun is simply a noun to which suru (する, "do") can be appended, while an adjectival noun is like a noun but uses -na (〜な) instead of -no (〜の) when acting attributively. Adjectives (i-adjectives) inflect identically to the negative form of verbs, which end in na-i (ない). Compare tabe-na-i (食べない, don't eat) → tabe-na-katta (食べなかった, didn't eat) and atsu-i (熱い, is hot) → atsu-katta (熱かった, was hot).

Some scholars, such as Eleanor Harz Jorden, refer to adjectives instead as adjectivals, since they are grammatically distinct from adjectives: they can predicate a sentence. That is, atsui (熱い) is glossed as "hot" when modifying a noun phrase, as in atsui gohan (熱いご飯, hot food), but as "is hot" when predicating, as in gohan wa atsui (ご飯は熱い, [the] food is hot).

The two inflected classes, verb and adjective, are closed classes, meaning they do not readily gain new members.^[1][2] Instead, new and borrowed verbs and adjectives are conjugated periphrastically as verbal noun + suru (e.g. benkyō suru (勉強する, do studying; study)) and adjectival noun + na. This differs from Indo-European languages, where verbs and adjectives are open classes, though analogous "do" constructions exist, including English "do a favor", "do the twist" or French "faire un footing" (do a "footing", go for a jog), and periphrastic constructions are common for other senses, like "try climbing" (verbal noun) or "try parkour" (noun). Other languages where verbs are a closed class include Basque: very few Basque verbs (albeits very common ones) have synthetic conjugation, all the others are only formed periphrastically. Conversely, pronouns are closed classes in Western languages but open classes in Japanese and some other East Asian languages.

In a few cases new verbs are created by appending -ru (〜る) suffix to a noun or using it to replace the end of a word. This is most often done with borrowed words, and results in a word written in a mixture of katakana (stem) and hiragana (inflectional ending), which is otherwise very rare.^[3] This is typically casual, with the most well-established example being sabo-ru (サボる, skip class; play hooky) (circa 1920), from sabotāju (サボタージュ, sabotage), with other common examples including memo-ru (メモる, write a memo), from memo (メモ), and misu-ru (ミスる, make a mistake) from misu (ミス, mistake). In cases where the borrowed word already ends with a ru (ル), this may be punned to a ru (る), as in gugu-ru (ググる, to google), from gūguru (グーグル, Google), and dabu-ru (ダブる, to double), from daburu (ダブル, double).^[4]

New adjectives are extremely rare; one example is kiiro-i (黄色い, yellow), from adjectival noun kiiro (黄色), and a more casual recent example is kimo-i (きもい, gross), by contraction of kimochi waru-i (気持ち悪い, bad-feeling).^[5] By contrast, in Old Japanese -shiki (〜しき) adjectives (precursors of present i-adjectives ending in -shi-i (〜しい), formerly a different word class) were open, as reflected in words like ita-ita-shi-i (痛々しい, pitiful), from the adjective ita-i (痛い, painful, hurt), and kō-gō-shi-i (神々しい, heavenly, sublime), from the noun kami (神, god) (with sound change). Japanese adjectives are unusual in being closed class but quite numerous – about 700 adjectives – while most languages with closed class adjectives have very few.^[6][7] Some believe this is due to a grammatical change of inflection from an aspect system to a tense system, with adjectives predating the change.

The conjugation of i-adjectives has similarities to the conjugation of verbs, unlike Western languages where inflection of adjectives, where it exists, is more likely to have similarities to the declension of nouns. Verbs and adjectives being closely related is unusual from the perspective of English, but is a common case across languages generally, and one may consider Japanese adjectives as a kind of stative verb.

Japanese vocabulary has a large layer of Chinese loanwords, nearly all of which go back more than one thousand years, yet virtually none of them are verbs or "i-adjectives" – they are all nouns, of which some are verbal nouns (suru) and some are adjectival nouns (na). In addition to the basic verbal noun + suru form, verbal nouns with a single-character root often experienced sound changes, such as -suru (〜する) → -zuru (〜ずる) (rendaku) → -jiru (〜じる), as in kin-jiru (禁じる, forbid), and some cases where the stem underwent sound change, as in tassuru (達する, reach), from tatsu (達).

Verbal nouns are uncontroversially nouns, having only minor syntactic differences to distinguish them from pure nouns like 'mountain'. There are some minor distinctions within verbal nouns, most notably that some primarily conjugate as -o suru (〜をする) (with a particle), more like nouns, while others primarily conjugate as -suru (〜する), and others are common either way. For example, keiken o suru (経験をする, to experience) is much more common than keiken suru (経験する), while kanben suru (勘弁する, to pardon) is much more common than kanben o suru (勘弁をする).^[8] Nominal adjectives have more syntactic differences versus pure nouns, and traditionally were considered more separate, but they, too, are ultimately a subcategory of nouns.

There are a few minor word classes that are related to adjectival nouns, namely the taru adjectives and naru adjectives. Of these, naru adjectives are fossils of earlier forms of na adjectives (the nari adjectives of Old Japanese), and are typically classed separately, while taru adjectives are a parallel class (formerly tari adjectives in Late Old Japanese), but are typically classed with na adjectives.

Japanese as a topic-prominent language

In discourse pragmatics, the term topic refers to what a section of discourse is about. At the beginning of a section of discourse, the topic is usually unknown, in which case it is usually necessary to explicitly mention it. As the discourse carries on, the topic need not be the grammatical subject of each new sentence.

Starting with Middle Japanese, the grammar evolved so as to explicitly distinguish topics from nontopics. This is done by two distinct particles (short words which do not change form). Consider the following pair of sentences:

In the first sentence the dog (犬, inu) is not a discourse topic—not yet; in the second sentence it is a discourse topic. In linguistics (specifically, in discourse pragmatics) a sentence such as the second one (with wa) is termed a presentational sentence because its function in the discourse is to present dog as a topic, to "broach it for discussion". Once a referent has been established as the topic of the current monolog or dialog, then in (formal) modern Japanese its marking will change from ga to wa.

To better explain the difference, the first sentence can be translated to "There's a dog eating a sandwich", while the second sentence can be translated to "You know the dog? It's eating a sandwich"; these renderings reflect a discourse fragment in which "the dog" is being established as the topic of an extended discussion. The first sentence answers the question "What is going on?," whereas the second sentence answers the question "What is the dog doing?"

Liberal omission of the subject of a sentence

The grammatical subject is commonly omitted in Japanese, as in

Subjects are mentioned when a topic is introduced, or in situations where an ambiguity might result from their omission. The preceding example sentence would most likely be uttered in the middle of a discourse, where who it is that "went to Japan" will be clear from what has already been said (or written).

Phrasal movement

In Japanese, phrasal constituents can be moved to the beginning or the end of the sentence. Leftward movement of a phrasal constituent is referred to as "scrambling".

Controversy over the characterization of nominal adjectives

Uehara (1998)^[9] observes that Japanese grammarians have disagreed as to the criteria that make some words inflectional and others not, in particular, the nominal adjectives – keiyōdōshi (形容動詞) or na-adjectives. (It is not disputed that nouns like hon 'book' are non-inflectional and that verbs and i-adjectives are inflectional.) The claim that nominal adjectives are inflectional rests on the claim that the element da, regarded as a copula by proponents of non-inflectional nominal adjectives, is really a suffix—an inflection. That is, kireida ('it is pretty') is a one-word sentence, not a two-word sentence, kirei da. However, numerous constructions show that da is less bound to the roots of nouns and nominal adjectives than -i and -(r)u are to the roots of i-adjectives and verbs, respectively.

(1) Reduplication for emphasis

Hora! Hon, hon! ('See! It is a book!')

Hora! Kirei, kirei! ('See! It is pretty!')

Hora! Furu-i, furu-i! ('See! It is old!') (the adjectival inflection -i cannot be left off)

Hora! Ik-u, ik-u! ('See! It does go!') (the verbal inflection -u cannot be left off)

(2) Questions. In Japanese, questions are formed by adding the particle ka (or in colloquial speech, just by changing the intonation of the sentence).^[10]

Hon ka? ('Is it a book?')

Kirei ka? ('Is it pretty?')

Furu-i ka? ('Is it old?) (-i cannot be left off)

Ik-u ka? ('Does it go?') (-u cannot be left off)

(3) Several epistemic modality predicates, e.g., mitai ('seem like')

Hon mitai da ('It seems to be a book')

Kirei mitai da ('It seems to be pretty')

Furu-i mitai da ('It seems to be old') (-i cannot be left off)

Ik-u mitai da ('It seems to go') (-u cannot be left off)

On the basis of such constructions, Uehara finds that the copula da is not suffixal and that nominal adjectives pattern with nouns in being non-inflectional.

Similarly, Eleanor Jorden considers this class of words a kind of nominal, not adjective, and refers to them as na-nominals in her textbook Japanese: The Spoken Language.

Grammatical case

Grammatical cases in Japanese are marked by particles placed after the nouns.^[11] A distinctive feature of Japanese is the presence of two cases which are roughly equivalent to the nominative case in other languages: one representing the sentence topic, other representing the subject. The most important case markers are the following:

• Nominative – ga (が) for subject, wa (は) for the topic
• Genitive – no (の)
• Dative – ni (に)
• Accusative – o (を)
• Lative – e (へ), used for destination direction (like in "to some place")
• Ablative – kara (から), used for source direction (like in "from some place")
• Instrumental/Locative– de (で)

Pronouns

Although many grammars and textbooks mention pronouns (代名詞, daimeishi), Japanese lacks true pronouns. (Daimeishi can be considered a subset of nouns.) Strictly speaking, linguistic pronouns do not take modifiers, but Japanese daimeishi do. For example, se no takai kare (背の高い彼, lit. "tall he") is valid in Japanese. Also, unlike true pronouns, Japanese daimeishi are not closed-class; new daimeishi are introduced and old ones go out of use relatively quickly.

A large number of daimeishi referring to people are translated as pronouns in their most common uses. Examples: kare (彼, he); kanojo (彼女, she); watashi (私, I); see also the adjoining table or a longer list.^[12] Some of these "personal nouns" such as onore (己, I (exceedingly humble)), or boku (僕, I (young male)), also have second-person uses: onore (おのれ) in second-person is an extremely rude "you", and boku in second-person is a diminutive "you" used for young boys. Kare and kanojo also mean "boyfriend" and "girlfriend" respectively, and this usage of the words is possibly more common than the use as pronouns.

Like other subjects, personal daimeishi are seldom used and are de-emphasized in Japanese. This is partly because Japanese sentences do not always require explicit subjects, and partly because names or titles are often used where pronouns would appear in a translation:

The possible referents of daimeishi are sometimes constrained depending on the order of occurrence. The following pair of examples from Bart Mathias^[13] illustrates one such constraint.

Reflexive pronouns

English has a reflexive form of each personal pronoun (himself, herself, itself, themselves, etc.); Japanese, in contrast, has one main reflexive daimeishi, namely jibun (自分), which can also mean 'I'. The uses of the reflexive (pro)nouns in the two languages are very different, as demonstrated by the following literal translations (*=impossible, ??=ambiguous):

If the sentence has more than one grammatical or semantic subject, then the target of jibun is the subject of the primary or most prominent action; thus in the following sentence jibun refers unambiguously to Shizuko (even though Makoto is the grammatical subject) because the primary action is Shizuko's reading.

In practice the main action is not always discernible, in which case such sentences are ambiguous. The use of jibun in complex sentences follows non-trivial rules.

There are also equivalents to jibun such as mizukara. Other uses of the reflexive pronoun in English are covered by adverbs like hitorideni which is used in the sense of "by oneself". For example,

Change in a verb's valency is not accomplished by use of reflexive pronouns (in this Japanese is like English but unlike many other European languages). Instead, separate (but usually related) intransitive verbs and transitive verbs are used. There is no longer any productive morphology to derive transitive verbs from intransitive ones, or vice versa.

Demonstratives

Demonstratives occur in the ko-, so-, and a- series. The ko- (proximal) series refers to things closer to the speaker than the hearer, the so- (medial) series for things closer to the hearer, and the a- (distal) series for things distant to both the speaker and the hearer. With do-, demonstratives turn into the corresponding interrogative form. Demonstratives can also be used to refer to people, for example

Demonstratives limit, and therefore precede, nouns; thus kono hon (この本) for "this/my book", and sono hon (その本) for "that/your book".

When demonstratives are used to refer to things not visible to the speaker or the hearer, or to (abstract) concepts, they fulfill a related but different anaphoric role. The anaphoric distals are used for shared information between the speaker and the listener.

Soko instead of asoko would imply that B does not share this knowledge about Sapporo, which is inconsistent with the meaning of the sentence. The anaphoric medials are used to refer to experience or knowledge that is not shared between the speaker and listener.

Again, ano is inappropriate here because Sato does not (did not) know Tanaka personally. The proximal demonstratives do not have clear anaphoric uses. They can be used in situations where the distal series sound too disconnected:

Stem forms

Conjugative suffixes and auxiliary verbs are attached to the stem forms of the affixee. In modern Japanese, there are six stem forms, ordered following from the -a, -i, -u, -e, -o endings that these forms have in 5-row (五段) verbs (according to the あ、い、う、え、お collation order of Japanese), where terminal and attributive forms are the same for verbs (hence only 5 surface forms), but differ for nominals, notably na-nominals.

Irrealis form (未然形, mizenkei) -a (and -ō)

is used for plain negative (of verbs), causative and passive constructions. The most common use of this form is with the -nai auxiliary that turns verbs into their negative (predicate) form. (See Verbs below.) The -ō version is used for volitional expression and formed by a euphonic change (音便, onbin).

Continuative form (連用形, ren'yōkei) -i

is used in a linking role (a kind of serial verb construction). This is the most productive stem form, taking on a variety of endings and auxiliaries, and can even occur independently in a sense similar to the -te ending. This form is also used to negate adjectives.

Terminal form (終止形, shūshikei) -u

is used at the ends of clauses in predicate positions. This form is also variously known as plain form (基本形, kihonkei) or dictionary form (辞書形, jishokei) – it is the form that verbs are listed under in a dictionary.

Attributive form (連体形, rentaikei) -u

is prefixed to nominals and is used to define or classify the noun, similar to a relative clause in English. In modern Japanese it is practically identical to the terminal form, except that verbs are generally not inflected for politeness; in old Japanese these forms differed. Further, na-nominals behave differently in terminal and attributive positions; see Adjectival verbs and nouns, below.

Hypothetical form (仮定形, kateikei) -e

is used for conditional and subjunctive forms, using the -ba ending.

Imperative form (命令形, meireikei) -e

is used to turn verbs into commands. Adjectives do not have an imperative stem form.

The application of conjugative suffixes to stem forms follow certain euphonic principles (音便, onbin).

Verbs

Verbs (動詞, dōshi) in Japanese are rigidly constrained to the end of a clause. This means that the predicate position is always located at the end of a sentence.

The subject and objects of the verb are indicated by means of particles, and the grammatical functions of the verb (primarily tense and voice) are indicated by means of conjugation. When the subject and the dissertative topic coincide, the subject is often omitted; if the verb is intransitive, the entire sentence may consist of a single verb. Verbs have two tenses indicated by conjugation, past and non-past. The semantic difference between present and future is not indicated by means of conjugation. Usually there is no ambiguity as context makes it clear whether the speaker is referring to the present or future. Voice and aspect are also indicated by means of conjugation, and possibly agglutinating auxiliary verbs. For example, the continuative aspect is formed by means of the continuative conjugation known as the gerundive or -te form, and the auxiliary verb iru ("to be"); to illustrate, miru (見る, "to see") → mite iru (見ている, "to be seeing").

Verbs can be semantically classified based on certain conjugations.

Stative verbs

indicate existential properties, such as "to be" (いる, iru), "to be able to do" (出来る, dekiru), "to need" (要る, iru), etc. These verbs generally do not have a continuative conjugation with -iru because they are semantically continuative already.

Continual verbs

conjugate with the auxiliary -iru to indicate the progressive aspect. Examples: "to eat" (食べる, taberu), "to drink" (飲む, nomu), "to think" (考える, kangaeru). To illustrate the conjugation, taberu (食べる, "to eat") → tabete iru (食べている, "to be eating").

Punctual verbs

conjugate with -iru to indicate a repeated action, or a continuing state after some action. Example: shiru (知る, "to know") → shitte iru (知っている, "to be knowing"); utsu (打つ, "to hit") → utte iru (打っている, "to be hitting (repeatedly)").

Non-volitional verb

indicate uncontrollable action or emotion. These verbs generally have no volitional, imperative or potential conjugation. Examples: konomu (好む, "to like / to prefer" [emotive]), mieru (見える, "to be visible" [non-emotive]).

Movement verbs

indicate motion. Examples: aruku (歩く, "to walk"), kaeru (帰る, "to return"). In the continuative form (see § Verbal adverbs) they take the particle ni to indicate a purpose.

There are other possible classes, and a large amount of overlap between the classes.

Lexically, nearly every verb in Japanese is a member of exactly one of the following three regular conjugation groups (see also Japanese godan and ichidan verbs).

Group 2a (上一段, kami ichidan, lit. upper 1-row)

verbs with a stem ending in -i. The terminal stem form always rhymes with -iru. Examples: miru (見る, "to see"), kiru (着る, "to wear").

Group 2b (下一段, shimo ichidan, lit. lower 1-row)

verbs with a stem ending in -e. The terminal stem form always rhymes with -eru. Examples: taberu (食べる, "to eat"), kureru (くれる, "to give" (to someone of lower or more intimate status)). (Some Group 1 verbs resemble Group 2b verbs, but their stems end in r-, not -e.)

Group 1 (五段, godan, lit. 5-row)

verbs with a stem ending in a consonant. When this is r- and the verb ends in -eru, it is not apparent from the terminal form whether the verb is Group 1 or Group 2b, e.g. kaeru (帰る, "to return"). If the stem ends in w-, that consonant sound only appears in before the final -a of the irrealis form.

The "row" in the above classification means a row in the gojūon table. "Upper 1-row" means the row that is one row above the center row (the u-row) i.e. i-row. "Lower 1-row" means the row that is one row below the center row (the u-row) i.e. e-row. "5-row" means the conjugation runs through all 5 rows of the gojūon table. A conjugation is fully described by identifying both the row and the column in the gojūon table. For example, miru (見る, "to see") belongs to ma-column i-row conjugation (マ行上一段活用), taberu (食べる, "to eat") belongs to ba-column e-row conjugation (バ行下一段活用), and kaeru (帰る, "to return") belongs to ra-column 5-row conjugation (ラ行五段活用).

One should avoid confusing verbs in ra-column 5-row conjugation (ラ行五段活用) with verbs in i-row conjugation (上一段活用) or e-row conjugation (下一段活用). For example, kiru (切る, "to cut") belongs to ra-column 5-row conjugation (ラ行五段活用), whereas its homophone kiru (着る, "to wear") belongs to ka-column i-row conjugation (カ行上一段活用). Likewise, neru (練る, "to knead") belongs to ra-column 5-row conjugation (ラ行五段活用), whereas its homophone neru (寝る, "to sleep") belongs to na-column e-row conjugation (ナ行下一段活用).

Historically, Classical Japanese had upper and lower 1-row groups (上・下一段, kami/shimo ichidan), upper and lower 2-row groups (上・下二段, kami/shimo nidan) and a 4-row group (四段, yodan). The nidan verbs became most of the ichidan verbs in modern Japanese (only a handful of kami ichidan verbs and a single shimo ichidan verb existed in classical Japanese). The yodan group was reclassified as the godan group during the post-WWII writing reform in 1946, to write Japanese as it is pronounced. Since verbs have migrated across groups in the history of the language, the conjugation of classical verbs cannot be ascertained from knowledge of modern Japanese alone.

Of the irregular classes, there are two:

sa-group

which has only one member, suru (する, "to do"). In Japanese grammars these words are classified as sa-hen (サ変), an abbreviation of sa-gyō henkaku katsuyō (サ行変格活用), sa-row irregular conjugation).

ka-group

which also has one member, kuru (来る, "to come"). The Japanese name for this class is ka-gyō henkaku katsuyō (カ行変格活用) or simply ka-hen (カ変).

Classical Japanese had two further irregular classes, the na-group, which contained shinu (死ぬ, "to die") and inu (往ぬ, "to go"/"to die"), the ra-group, which included such verbs as ari (あり), the equivalent of modern aru, as well as quite a number of extremely irregular verbs that cannot be classified.

The following table illustrates the stem forms of the above conjugation groups, with the root indicated with dots. For example, to find the hypothetical form of the group 1 verb kaku (書く), look in the second row to find its root, kak-, then in the hypothetical row to get the ending -e, giving the stem form kake. When there are multiple possibilities, they are listed in the order of increasing rarity.

1. The -a and -o irrealis forms for Group 1 verbs were historically one, but since the post-WWII spelling reforms they have been written differently. In modern Japanese the -o form is used only for the volitional mood and the -a form is used in all other cases; see also the conjugation table below.
2. The unexpected ending is due to the verb's root being tsukaw- but w- only being pronounced before -a in modern Japanese.

The above are only the stem forms of the verbs; to these one must add various verb endings in order to get the fully conjugated verb. The following table lists the most common conjugations. Note that in some cases the form is different depending on the conjugation group of the verb. See Japanese verb conjugations for a full list.

1. This is an entirely different verb; suru (する) has no potential form.
2. These forms change depending on the final syllable of the verb's dictionary form (whether u, ku, gu, su, etc.). For details, see Euphonic changes, below, and the article Japanese verb conjugation.

The polite ending -masu conjugates as a group 1 verb, except that the negative imperfective and perfective forms are -masen and -masen deshita respectively, and certain conjugations are in practice rarely if ever used. The passive and potential endings -reru and -rareru, and the causative endings -seru and -saseru all conjugate as group 2b verbs. Multiple verbal endings can therefore agglutinate. For example, a common formation is the causative-passive ending: -sase-rareru.

As should be expected, the vast majority of theoretically possible combinations of conjugative endings are not semantically meaningful.

Adjectival verbs and nouns

Semantically speaking, words that denote attributes or properties are primarily distributed between two morphological classes (there are also a few other classes):

• adjectival verbs (形容詞, keiyōshi, conventionally called "i-adjectives")– these have roots and conjugating stem forms, and are semantically and morphologically similar to stative verbs.
• adjectival nouns (形容動詞, keiyōdōshi, lit. "adjectival verb", conventionally called "na-adjectives")– these are nouns that combine with the copula.

Unlike adjectives in languages like English, i-adjectives in Japanese inflect for aspect and mood, like verbs. Japanese adjectives do not have comparative or superlative inflections; comparatives and superlatives have to be marked periphrastically using adverbs like motto ('more') and ichiban ('most').

Every adjective in Japanese can be used in an attributive position, and nearly every Japanese adjective can be used in a predicative position. There are a few Japanese adjectives that cannot predicate, known as rentaishi (連体詞, attributives), which are derived from other word classes; examples include ōkina (大きな, "big"), chiisana (小さな, "small"), and okashina (おかしな, "strange") which are all stylistic na-type variants of normal i-type adjectives.

All i-adjectives except for ii (いい, good) have regular conjugations, and ii is irregular only in the fact that it is a changed form of the regular adjective yoi (良い) permissible in the terminal and attributive forms. For all other forms it reverts to yoi.

1. The attributive and terminal forms were formerly .ki (安き) and .shi (安し), respectively; in modern Japanese these are used productively for stylistic reasons only, although many set phrases such as nanashi (名無し, anonymous) and yoshi (よし, [general positive interjection], sometimes written yosh), derive from them.
2. The imperative form is extremely rare in modern Japanese, restricted to set patterns like osokare hayakare (遅かれ早かれ, 'sooner or later'), where they are treated as adverbial phrases. It is impossible for an imperative form to be in a predicate position.

Common conjugations of adjectives are enumerated below. ii is not treated separately, because all conjugation forms are identical to those of yoi.

1. Note that these are just forms of the i-type adjective nai (ない)
2. Since most adjectives describe non-volitional conditions, the volitional form is interpreted as "it is possible", if sensible. In some rare cases it is semi-volitional: yokarō (良かろう, 'OK', lit: "let it be good") in response to a report or request.

Adjectives too are governed by euphonic rules in certain cases, as noted in the section on it below. For the polite negatives of na-type adjectives, see also the section below on the copula da (だ).

Copula (だ da)

The copula da behaves very much like a verb or an adjective in terms of conjugation.

Note that there are no potential, causative, or passive forms of the copula, just as with adjectives.

The following are some examples.

ジョンは学生だ。

JON wa gakusei da

"John is a student."

明日も晴れなら、ピクニックしよう。

Ashita mo hare nara, PIKUNIKKU shiyō

"If tomorrow is clear too, let's have a picnic."

In continuative conjugations, de wa (では) is often contracted in speech to ja (じゃ); for some kinds of informal speech ja is preferable to de wa, or is the only possibility.

Euphonic changes (音便, onbin)

Adverbs

Adverbs in Japanese are not as tightly integrated into the morphology as in many other languages; adverbs are not an independent class of words, but the role of an adverb is played by other words. For example, every adjective in the continuative form can be used as an adverb; thus, yowai (弱い, 'weak' [adj]) → yowaku (弱く, 'weakly' [adv]). The primary distinguishing characteristic of adverbs is that they cannot occur in a predicate position, just as it is in English. The following classification of adverbs is not intended to be authoritative or exhaustive.

Verbal adverbs

verbs in the continuative form with the particle ni. E.g. miru (見る, 'to see') → mi ni (見に, 'for the purpose of seeing'), used for instance as: mi ni iku (見に行く, 'go to see (something)').

Adjectival adverbs

adjectives in the continuative form, as mentioned above. Example: yowai (弱い, 'weak' [adj]) → yowaku (弱く, 'weakly' [adv])

Nominal adverbs

grammatical nouns that function as adverbs. Example: ichiban (一番, 'most highly').

Sound symbolism

words that mimic sounds or concepts. Examples: kirakira (きらきら, 'sparklingly'), pokkuri (ぽっくり, 'suddenly'), surusuru (するする, 'smoothly' (sliding)), etc.

Often, especially for sound symbolism, the particle to (と, 'as if') is used. See the article on Japanese sound symbolism.

Conjunctions and interjections

Although called "conjunctions", conjunctions in Japanese are – as their English translations show – actually a kind of adverb:

Examples of conjunctions: soshite (そして, 'and then'), mata (また, 'and then/again'), etc.

Interjections in Japanese differ little in use and translation from interjections in English:

Examples of interjections: hai (はい, yes/OK/uh), hē (へえ, wow!), iie (いいえ, no/no way), oi (おい, hey!), etc.

Particles

Particles in Japanese are postpositional, as they immediately follow the modified component. Both the pronunciation and spelling differs for the particles wa (は), e (へ) and o (を), and are romanized according to pronunciation rather than spelling. Only a few prominent particles are listed here.