Japanese conjugation

Japanese conjugation, like the conjugation of verbs of many other languages, allows verbs to be morphologically modified to change their meaning or grammatical function. In Japanese, the beginning of a word is preserved during conjugation, while the ending of the word is altered in some way to change the meaning. Japanese verb conjugations are independent of person, number and gender ; the conjugated forms can express meanings such as negation, present and past tense, volition, passive voice, causation, imperative and conditional mood, and ability. There are also special forms for conjunction with other verbs, and for combination with particles for additional meanings.
Japanese verbs have agglutinating properties: some of the conjugated forms are themselves conjugable verbs, which can result in several suffixes being strung together in a single verb form to express a combination of meanings.

Verb groups

For Japanese verbs, the verb stem remains invariant among all conjugations. However, conjugation patterns vary according to a verb's category. For example, and belong to different verb categories and therefore follow different conjugation patterns. As such, knowing a verb's category is essential for conjugating Japanese verbs.
Japanese verbs can be allocated into three categories:

, also known as "pentagrade verbs"
, also known as "monograde verbs"
Irregular verbs, most notably: and

Verbs are conjugated from their "dictionary form", where the final kana is either removed or changed in some way. From a technical standpoint, verbs usually require a specific conjugational stem for any given inflection or suffix. With godan verbs, the conjugational stem can span all five columns of the gojūon kana table. Ichidan verbs are simpler to conjugate: the final kana, which is always, is simply removed or replaced with the appropriate inflectional suffix. This means ichidan verb stems, in themselves, are valid conjugational stems which always end with the same kana.
This distinction can be observed by comparing conjugations of the two verb types, within the context of the gojūon table.
As can be seen above, the godan verb has a static verb stem,, and a dynamic conjugational stem which changes depending on the purpose:,,, and. Unlike godan verb stems, ichidan verb stems are also functional conjugational stems, with the final kana of the stem remaining static in all conjugations.

Verb bases

Conjugable words are traditionally considered to have six possible. However, as a result of the language evolving, historical sound shifts, and the post‑WWII spelling reforms, three additional sub‑bases have emerged for verbs. Meanwhile, verbs no longer differentiate between the and the bases. Verb bases function as the necessary stem forms to which inflectional suffixes attach.
The "default" dictionary form, or lemma, of any conjugational morpheme, be it a verb, an adjective or an auxiliary, is its conclusive form, which is listed first in the table below. The verb group determines how to derive any given conjugation base for the verb. With godan verbs, the base is derived by shifting the final kana along the respective vowel row of the gojūon kana table. With ichidan verbs, the base is derived by removing or replacing the final kana.
The table below illustrates the various verb bases across the verb groups, with the patterns starting from the dictionary form. The mizenkei base for verbs ending in appears to be an exceptional case with the unexpected. This realization of is a leftover from past sound changes, an artifact preserved from the archaic Japanese from verbs. This is noted with historical kana orthography in dictionaries; for example, from from and from . In modern Japanese, original instances of mid‑word consonant have since been dropped before all vowels except ..

Of the nine verb bases, the [|shūshikei/rentaikei], [|meireikei], and ren'yōkei bases can be considered fully conjugated forms without needing to append inflectional suffixes. In particular, the shūshikei/rentaikei and meireikei bases do not conjugate with any inflectional suffixes. By contrast, a verb cannot be considered fully conjugated in its kateikei, mizenkei, ishikei, kanōkei, or onbinkei base alone; a compatible inflectional suffix is required for that verb construction to be grammatical.
Certain inflectional suffixes, in themselves, take on the form of verbs or i‑adjectives. These suffixes can then be further conjugated by adopting one of the verb bases, followed by the attachment of the appropriate suffix. The agglutinative nature of Japanese verb conjugation can thus make the final form of a given verb conjugation quite long. For example, the word is broken down into its component morphemes below:

Derivative verb bases

There are three modern verb base forms that are considered to be derived from older forms. These are the potential, hortative, 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, which was also used to express the passive voice and the spontaneous voice. This evolved into the modern passive ending, 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 +, and also via the kanōkei base. 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 of the Classical Japanese of the time. 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 was also used to express the hortative mood for in Old Japanese and Middle Japanese, in combination with hortative suffix. Sound changes caused the resulting ‑amu ending to change: → → → →. The post‑WWII spelling reforms updated spellings to reflect this and other sound changes, resulting in the addition of the ishikei or hortative base, ending with, for the hortative mood of yodan verbs. This also resulted in a reclassification of "yodan verbs" to.
The ren'yōkei base also underwent various euphonic changes specific to the perfective and infinitive forms for certain verb stems, giving rise to the onbinkei or euphonic base. In the onbinkei base, the inflectional suffixes for godan verbs vary according to the last kana of the verb's ren'yōkei base.

The bases of ''suru''

Unlike most verbs, suru and its derived compounds exhibit strong irregularity in their verb bases. In some cases, some variants are preferred over the others, and such preferences vary among speakers. Roughly speaking, there are three major groups that behave similarly:

Group A: Suru itself and compounds of it and free nouns :,,,,, etc.
Group B: Compounds with bound Sino-Japanese morphemes that behave more like godan verbs. These often have full-fledged, interchangeable godan derivatives:,,, etc.
:Such a form as is supposed to be the classical Japanese equivalent to. Compare the following translations of 1 John 3:14 :
:::1917 classical:
:::1955 modern:
:However, aisenu as the negative of aisu would likely be confused with aisenu as the negative of the potential aiseru in modern Japanese. It is clear that aisenu is not the same as aisanu where they both occur in close proximity:.
:There is great variety among Group-B verbs as to whether to choose between the godan-negative ‑san/‑zu and the classical-negative ‑sen/‑zu, and there are indeed cases where only contexts can clarify whether ‑sen/‑zu are truly classical-negative, or actually godan-negative-potential. In general, it seems that if the Sino-Japanese stem contains a moraic obstruent as in, a moraic nasal as in, or lengthening mora as in, the godan options are less preferable with all auxiliaries, though not impossible. Thus, such forms as are more likely to be classical-negative, while such forms as are more likely to be godan-negative-potential; and while both and are unambiguously godan-negative, the former are not as likely as the latter.
Group C: Compounds with bound Sino-Japanese morphmes that behave more like upper ichidan verbs. These often have full-fledged, interchangeable upper ichidan derivatives:,,,, etc.
Group D: Compounds with bound Sino-Japanese morphemes that behave more like lower ichidan verbs. These may have full-fledged, interchangeable lower ichidan derivatives: and.

Across the following forms of suru within standard Japanese, an eastern dialect, while there is a dominance of the eastern vowel i as in shinai, shiyō and shiro, the once prestigious western vowel e, as in sen and seyo, still has currency especially in formal or literary Japanese. Such variants as senai and sanai ; shin ; shō, seyō and sō ; sero ; and shiyo, sē and sei, remain dialectal or obsolete.


Irrealis	se shi sa	benkyō se benkyō shi benkyō sa	aisa aise aishi	tasse tasshi tassa	sasse sasshi	shinji shinze	shinze shinji
Passive	sareru serareru shirareru	benkyō sareru benkyō serareru benkyō shirareru	aisareru aiserareru aishirareru	tasserareru tasshirareru tassareru	sasserareru sasshirareru	shinjirareru shinzerareru	shinzerareru shinjirareru
Potential	dekiru	benkyō dekiru	aiseru aisereru aishireru aisuru koto ga dekiru aisu koto ga dekiru	tassereru tasshireru tasseru tassuru koto ga dekiru tassu koto ga dekiru	sassereru sasshireru sassuru koto ga dekiru sasshiru koto ga dekiru	shinjireru shinzereru shinjiru koto ga dekiru shinzuru koto ga dekiru	shinzereru shinjireru shinzuru koto ga dekiru shinzeru koto ga dekiru shinjiru koto ga dekiru
Causative	saseru sesaseru shisaseru	benkyō saseru benkyō sesaseru benkyō shisaseru	aisaseru aisesaseru aishisaseru	tassesaseru tasshisaseru tassaseru	sassesaseru sasshisaseru	shinjisaseru shinzesaseru	shinzesaseru shinjisaseru
Negative	shinai senu	benkyō shinai benkyō senu	aisanai aishinai aisanu aisenu	tasshinai tassanai tassenu tassanu tasshinu	sasshinai sassenu sasshinu	shinjinai shinjinu shinzenu	shinjinai shinzenai shinzenu shinjinu
Hortative	shiyō	benkyō shiyō	aisō aishiyō	tasshiyō tassō	sasshiyō	shinjiyō	shinjiyō shinzeyō
Infinitive	shi	benkyō shi	aishi	tasshi	sasshi	shinji	shinji shinze
Attributive/conclusive	suru	benkyō suru	aisuru aisu	tassuru tassu tasshiru	sassuru sasshiru	shinjiru shinzuru	shinzuru shinzeru shinjiru
Attributive/conclusive + beki	su beki	benkyō su beki	aisu beki	tassu beki tasshiru beki	sassu beki sasshiru beki	shinjiru beki shinzu beki	shinzu beki shinzeru beki shinjiru beki
Conditional	sureba	benkyō sureba	aisureba aiseba	tassureba tasseba tasshireba	sassureba sasshireba	shinjireba shinzureba	shinzureba shinzereba shinjireba
Imperative	shiro seyo	benkyō shiro benkyō seyo	aise aishiro aiseyo	tasshiro tasseyo tasshiyo tasse	sasshiro sasseyo sasshiyo	shinjiro shinjiyo shinzeyo	shinjiro shinzero shinzeyo shinjiyo