Derivative verb bases

There are three modern verb base forms that are considered to be derived from older forms. These are the potential, volitional, and euphonic sub‑bases, as shown in the Verb base formation table above.

As with all languages, the Japanese language has evolved to fulfil the contemporary needs of communication. The potential form of verbs is one such example. In Old Japanese and Early Middle Japanese, potential was expressed with the verb ending ゆ (yu), which was also used to express the passive voice ("to be done") and the spontaneous voice ("something happens on its own"). This evolved into the modern passive ending （ら）れる (-(ra)reru), which can similarly express potential and spontaneous senses. As usage patterns changed over time, different kinds of potential constructions emerged, such as the grammatical pattern of the rentaikei base + -koto ga dekiru (〜ことができる), and also via the kanōkei base.^[4] The historical development of the kanōkei base is disputed, however the consensus is that it stemmed from a shift wherein transitive verbs developed an intransitive sense similar to the spontaneous, passive, and potential, and these intransitive forms conjugated in the 下二段活用 (shimo nidan katsuyō, lower bigrade conjugation pattern) of the Classical Japanese of the time.^[5] The lower bigrade conjugation pattern evolved into the modern ichidan pattern in modern Japanese, and these stems for godan verbs have the same form as the hypothetical stems in the table above.

The mizenkei base that ends with -a was also used to express the volitional mood for yodan verbs (四段動詞, yodan-dōshi, "Class‑4 verbs") in Old Japanese and Middle Japanese, in combination with volitional suffix む (-mu). Sound changes caused the resulting -amu ending to change: /-amu/ → /-ãu/ → /-au/ (like English "ow") → /-ɔː/ (like English "aw") → /-oː/. The post‑WWII spelling reforms updated spellings to reflect this and other sound changes, resulting in the addition of the ishikei or volitional base, ending with -o, for the volitional mood of yodan verbs. This also resulted in a reclassification of "yodan verbs" to "godan verbs" (五段動詞, godan-dōshi, "Class‑5 verbs").^[8][15]

The ren'yōkei base also underwent various euphonic changes specific to the perfective and conjunctive (te) forms for certain verb stems,^[26][6][7] giving rise to the onbinkei or euphonic base.^[17] In the onbinkei base, the inflectional suffixes for godan verbs vary according to the last kana of the verb's ren'yōkei base.^[2]

Copula: Conjugation table

The Japanese copula is not a standard 'verb' and conjugations are limited to a smaller subset of functions. Furthermore, this conjugates according to its own specific patterns:^[10]

^[i] じゃ (ja) is a colloquial abbreviation of では (de wa).^[10]

^[ii] Although だろう (darō) and でしょう (deshō) were originally conjugations of だ (da) and です (desu) respectively, they are now also used as auxiliary verbs.^[28]

Copula: Grammatical compatibility

The だ negative forms, じゃない (ja nai) and ではない (de wa nai), are compatible with all negative valence conjugations (such as the negative past tense or the negative -te form).^[10] However, the です negative forms, じゃありません (ja arimasen) and ではありません (de wa arimasen), are conjugated into the past tense by appending でした (deshita) as a suffix (and are therefore incompatible with subsequent 〜ない (-nai) conjugations).^[10] Furthermore, the perfective forms, だった (datta) and でした (deshita), are compatible with the ~tara conditional.^[29]

Imperfective: Conjugation table

The imperfective form uses the shūshikei/rentaikei base, and is thus equivalent to the dictionary form.

^[i] For godan verbs ending in 〜る (-ru), the imperfective conjugation, or dictionary form, is the simplest form which is syncretic with ichidan verbs.

Imperfective: Grammatical compatibility

The imperfective form can be used to issue prohibitive commands by attaching 〜な (-na).^[31] For example, 入るな！ (hairu na!, "Do not enter!"). Additionally, the imperfective form is compatible with the nominalizers 〜の (-no) and 〜こと (-koto), which repurpose the verb as a noun. For example, カラオケで歌うのは楽しい！ (karaoke de utau no wa tanoshii!, Singing at karaoke is fun!).

Negative: Conjugation table

The negative form is created by using the mizenkei base, followed by the ない (nai) suffix.

^[i] For godan verbs ending in 〜う (-u), the "う" changes to "わ" (wa) in the negative conjugation. It does not change to "あ" (a).

^[ii] The negative past form of 〜ます is 〜ませんでした (-masen deshita, did not).^[2]

Negative: Grammatical compatibility

The negative form is compatible with the ～で (-de) particle for additional functions, such as requesting someone to cease/desist or joining a subordinate clause.

It is also compatible with i‑adjective inflections, since the ～ない (-nai) suffix ends with ～い (-i).

Negative continuous

The negative continuous form is created by using the mizenkei base, followed by the 〜ず (zu) suffix; equivalent to replacing 〜ない (-nai) with 〜ず (-zu) in the table above. An exception is する (suru, to do), which instead conjugates as せず (sezu, not doing). In this form, the negative continuous cannot terminate a sentence. The verb has the "negative continuous tense" unless followed by the に (ni) particle, where its meaning changes to "without". The -zuni form (〜ずに, without doing) is semantically interchangeable with -naide (〜ないで, without doing). However, -zuni is only used in written Japanese or formal speech.^[32][33]

Perfective: Conjugation table

The perfective form is created by using the onbinkei base, followed by the た・だ (ta/da) suffix. This conjugation pattern is more complex compared to other conjugations because the exact realization of the inflectional suffix—particularly in godan verbs—is based on the euphony (音便, onbin) of the verb stem. (See also: Euphonic changes)

^[i] 死ぬ (shinu, to die) is the only verb with the ぬ (nu) suffix, in the entire Japanese vocabulary.

^[ii] The negative perfective form of 〜ます is 〜ませんでした (-masen deshita, did not).^[2]

Perfective: Grammatical compatibility

The perfective form is compatible with:

• The "tari form" (or "tari‑tari form", also known as the "tari‑tari‑suru form"), to describe a non‑exhaustive list of actions (similar to ＡやＢ describes a non‑exhaustive lists of objects). It uses り (ri) as the subordinate conjunction.^[35][36]
• The "tara form" (or "past conditional"), to describe events that will happen as a result of completing something. It uses ら (ra) as the subordinate conjunction.^[37][29]
  • It can be used to mean "if" or "when";
  • It can also be used to reveal an unexpected outcome that happened in the past.

te form: Conjugation table

The te form is created by using the onbinkei base, followed by the て・で (te/de) suffix. Just like the perfective form, this conjugation pattern is more complex compared to other conjugations because the exact realization of the inflectional suffix—particularly in godan verbs—is based on the euphony (音便, onbin) of the verb stem. (See also: Euphonic changes)

^[i] 死ぬ (shinu, to die) is the only verb with the ぬ (nu) suffix, in the entire Japanese vocabulary.

^[ii] This conjugation is not reciprocated in the perfective form; the past tense of ない (-nai) is なかった (-nakatta, was not).

^[iii] The 〜ないで (-nai de) form is only grammatical with verbs. It is used to emphasize negation, or otherwise used as an imperative if an auxiliary follows, e.g. 〜ないで下さい (-nai de kudasai, Please don't…).^[32]

^[iv] The 〜なくて (-nakute) form is grammatical with adjectives and copula, but also with verbs when expressing a consequential human emotion or contradiction.^[32]

te form: Grammatical compatibility

The te form is compatible with particles for additional functions, such as giving permission or expressing prohibition.^[41][39]

The te form is also compatible with an extensive list of auxiliary verbs. These auxiliary verbs are attached after the 〜て.^[42]

^[v] Colloquially, the い (i) is dropped. For example, 持っている (motte iru) becomes 持ってる (motte ru).

^[vi] Colloquially, てお〜 (te o-) undergoes morpheme fusion, becoming と〜 (to-). For example, 作っておく (tsukutte oku) becomes 作っとく (tsukuttoku).

^[vii] In this case, て is dropped rather than being attached to ちゃう. This is because ちゃう (chau) is a morpheme fusion of ちまう (chimau), which itself is a morpheme fusion of てしまう (te shimau). Similarly, で (de) is also dropped when attaching to じゃう (jau) and じまう (jimau), which are the morpheme fusions of でしまう (de shimau).^[43]

Finally, the te form is necessary for making polite requests with 下さる (kudasaru) and くれる (kureru). These honorific words are attached with their imperative forms 〜下さい (-kudasai) and 〜くれ (-kure), which is more socially proper than using the true imperative.^[44][42]

te form: Advanced usage

During speech, the speaker may terminate a sentence in the te form but slightly lengthen the vowel sound as a natural pause: てぇ (te…). Similar to when a sentence ends with "so…" in English, this serves as a social cue that can:

• give the listener a moment to process;
• indicate the speaker is not finished speaking;
• seek permission from the listener to continue;
• imply that the listener should infer the remainder of the sentence.

Another usage of the te form is, just as with English, the order of clauses may be reversed to create emphasis. However, unlike in English, the sentence will terminate on the te form (rather than between clauses).

Conjunctive: Conjugation table

The conjunctive form uses the ren'yōkei base. It is one of the simplest conjugation patterns due to its lack of irregular conjugations. It does have an additional case for certain honorific verbs, but even those follow a consistent conjugation pattern.

^[i] The English translations use the "-ing" suffix for nominalization. Therefore, they are nouns, not present continuous verbs.

^[ii] Other honorific words, such as ござる (gozaru, to be), いらっしゃる (irassharu, to come/go) and なさる (nasaru, to do), also conjugate with this pattern.^[2]

Conjunctive: Grammatical compatibility

The conjunctive form is compatible with particles for additional functions, such as expressing purpose^[49] or a firm avoidance.^[50]

The conjunctive form is also compatible with an extensive list of auxiliary verbs.^[46] One of which, ます (masu), has highly irregular inflections.^[51][52][53]

Conjunctive: Advanced usage

The conjunctive form, like the te form, connects clauses in a similar way to how "and" does in English. However, the conjunctive and te forms are not usually interchangeable, and each form fulfills specific grammatical purposes. When a pair of verbs have a strong connection in context, only the te form can bridge them. When a pair of verbs are not directly related but happen during a shared period of time, only the conjunctive form can bridge them. Furthermore, if a pair of verbs are both controllable or uncontrollable in nature, the te form must bridge them; otherwise, when a verb is controllable whilst the other verb is uncontrollable, the conjunctive form must bridge them. Finally, the te and conjunctive forms are interchangeable if additional information is included between the verbs.^[40][39]

In the case where the conjunctive form is interchangeable with the te form, there is a stylistic means where the conjunctive form is preferred. This avoids 「て…て…て…」 (te…te…te…) repetition, much like how English users might avoid saying "and…and…and…". In practice however, such a strategy is more readily accustomed to writing and more difficult to control in spoken conversation (where the te form is usually elected for every verb).^[40]

Another common usage is to form compound words, specifically compound nouns and compound verbs. As for compound nouns, the conjunctive form attaches as a prefix to another noun. Compound verbs are formed in the same way, except the conjunctive form attaches to the imperfective form. This pattern can be used to express mutuality if a transitive verb attaches to 〜合う (-au, to unite).^[54]

The conjunctive form is also used in formal honorifics, such as お使い下さい (o tsukai kudasai, "Please use this.").

Volitional: Conjugation table

The volitional form is created by using the ishikei base, followed by the う・よう (u/yō) suffix. Phonetically, う is surfaced as お (o) in volitional form, unlike う in dictionary/imperfective form; for example, 問う (tou, to ask) and 問おう (toō, let's ask).

^[i] Theoretical conjugation only; it's unnatural and not usually used.^[2]

Volitional: Grammatical compatibility

The volitional form is also used to describe intention 〜と思う (-to omou)^[57] an attempt 〜とする (-to suru) or an imminent action 〜としている (-to shite iru).^[58]

Passive: Conjugation table

The passive form is created by using the mizenkei base, followed by the れる・られる (reru/rareru) suffix. For ichidan verbs and 来る (kuru), the passive form and the potential form have an identical conjugation pattern with the same られる (rareru) suffix. This makes it impossible to distinguish whether an ichidan verb adopts a passive or potential function without contextual information.

^[i] For godan verbs ending in 〜る (-ru), the passive conjugation is syncretic with ichidan verbs.

^[ii] For godan verbs ending in 〜う (-u), the "う" changes to "わ" (wa) in the passive conjugation. It does not change to "あ" (a).^[60]

^[iii] Theoretical conjugation only; it's unnatural and not usually used.^[2]

Passive: Grammatical compatibility

After conjugating into the passive form, the verbs become ichidan verbs. They can therefore be further conjugated according to any ichidan pattern. For instance, a passive verb (e.g. 言われる (iwareru, be said)) can conjugate using the ichidan pattern for the te form (て形, te kei) to join sequential statements (言われて (iwarete)), or the conjunctive form to append the polite -masu (〜ます) auxiliary verb (言われます (iwaremasu)).

Causative: Conjugation table

The causative form is created by using the mizenkei base, followed by the せる・させる (seru/saseru) suffix.

^[ii] The causative form has a shortened variation, where the 〜せる (-seru) suffix undergoes morpheme fusion and becomes 〜す (-su); however, the short form is less commonly used than the standard conjugation.^[62]

^[iii] For godan verbs ending in 〜う (-u), the "う" changes to "わ" (wa) in the causative conjugation. It does not change to "あ" (a).^[61]

^[iv] Theoretical conjugation only; it's unnatural and not usually used.^[2]

Causative: Grammatical compatibility

After conjugating into the causative form, the verbs become ichidan verbs. They can therefore be further conjugated according to any ichidan pattern. For instance, a causative verb (e.g. 言わせる (iwaseru, caused to say)) can conjugate using the ichidan pattern for the te form (て形, te kei) to join sequential statements (言わせて (iwasete)), or the conjunctive form to append the polite -masu (〜ます) auxiliary verb (言わせます (iwasemasu)).

Causative passive

The causative passive form expresses that a reluctant subject was positioned (or forced) into doing something they would rather avoid. The causative passive form is obtained by conjugating a verb into its causative form and further conjugating it into the passive form. However, because words such as 待たせられる (mataserareru) are considered difficult to pronounce, the conjugational suffix is often contracted in colloquial speech. Specific to godan verbs only, the せら〜 (sera-, from せられる) contracts into さ〜 (sa-).^[63]

Imperative: Conjugation table

The imperative form uses the meireikei base.

^[i] 〜ろ (-ro) is used for the spoken imperative form, while 〜よ (-yo) is used for the written imperative form.^[19]

^[ii] Theoretical conjugation only; it's unnatural and not usually used.^[2]

Non‑volitional verbs, such as 分かる (wakaru, to understand) and できる (dekiru, to be able), have imperative forms (for these two verbs, 分かれ (wakare) and できろ (dekiro)), but these appear to be relatively recent innovations, and usage may be limited to informal contexts.

Potential: Conjugation table

The potential form is created by using the kanōkei base, followed by the る・(ら)れる (ru/(ra)reru) suffix. する (suru, to do) has its own suppletive potential form 出来る (dekiru, can do). For ichidan verbs and 来る (kuru), the potential form and the passive form have an identical conjugation pattern with the same られる (rareru) suffix. This makes it impossible to distinguish whether an ichidan verb adopts a passive or potential function without contextual information.

However, in colloquial speech the ら (ra) is removed from られる (rareru) in a phenomenon known as ら抜き言葉 (ranuki kotoba).^[64] For example, こられる (korareru, can come) becomes これる (koreru). This contraction is specific to the potential form, and is not reciprocated in the passive form.