Japanese Verbs and Tenses 日本語の動詞と時制
Japanese verb conjugations are interesting. See the list of Japanese verb conjugations. Almost all of these are regular, but there are a few Japanese irregular verbs, and the conjugations of the few irregular verbs are also listed. Japanese verb conjugation is the same for all subjects, first person ("I", "we"), second person ("you") and third person ("he/she/it" and "they"), singular and plural. The present plain form (the dictionary form) of all verbs ends in u. In modern Japanese, there are no verbs that end in fu, pu, or yu, no verbs ending in zu other than certain する forms (such as 禁ず kin-zu), and 死ぬ (しぬ, shinu; to die) is the only one ending in nu in the dictionary form.
When a verb is conjugated it adopts a so called "form". Forms change depending on the tense, mode, and suffix of the verb's stem. The stem of the verb is the prefix that is unchanging in the conjugation.
For example in the following infinitive (aka dictionary) forms of these verbs the stem is in bold:
iku (行く): To go
taberu (食べる) To eat
Verb conjugates are often grouped into two categories, according to whether the last letter of the stem is a vowel or consonant (when romanized)
Type I: consonant-stems (五段動詞, godandōshi), and
Type II: vowel-stems (一段動詞, ichidandōshi, いる iru,える eru forms).
For conjugating type I verbs the suffix of the infinitive form is replaced by a different sound according to the original suffix, then a suffix which is consistent by tense is added.
The infinitive form of a type I verb has an う u sound (u, tsu, ru, ku, gu, nu, bu, mu, su)
The polite ～ます -masu form has an い i sound (i, chi, ri, ki, gi, ni, bi, mi, shi)
The negative form has an あ a sound (wa, ta, ra, ka, ga, na, ba, ma, sa)
The potential form has an え e sound (e, te, re, ke, ge, ne, be, me, se)
The volitional form has an おう ō sound (ō, tō, rō, kō, gō, nō, bō, mō, sō).