Japanese Consonant and Vowel Verbs - Terminology

Terminology

The terms "consonant-stem" and "vowel-stem" come from considering the invariant part of the verb (the verb stem) on the basis of phonemes – concretely, by writing in rōmaji. This is an abstract perspective, as the consonant stem itself never occurs independently, but only with a following vowel, as Japanese words are formed of morae – concretely, writing in kana. For example, while the stem of yomu is yom-, the bare *yom is not an independent word.

The standard Japanese terms, ichidan and godan, literally "one row" and "five rows", more formally unigrade and quinquegrade, correspond to the number of different morae (kana) that appear in the stem forms of the verb, which are then optionally combined with a suffix to form a conjugated word. Formally, verbs are classified by which column of the gojūon their stem ends in, with vowel stem verbs further distinguished into i and e type. For example, 読む yomu is of マ行五段活用 ma-gyō go-dan katsuyō "ma-column five-row conjugation" type, as its stem form end in each of the five rows of the ま column, namely まみむめも:

• 読ま よま yoma- as in yomanai (negative, irrealis),
• 読み よみ yomi- as in yomimasu (polite non-past),
• 読む よむ yomu- as in yomu (plain non-past; dictionary form),
• 読め よめ yome- as in yomeba (conditional),
• 読も よも yomo- as in yomō (yomou) (hortative/volitional).

Note that the volitional o stem is historically the negative a stem with euphonic sound change – and the o stem is only used for the volitional form – so these verbs were traditionally called 四段 yodan "four-row, quadrigrade", omitting the o form.

While the above uses are the most common uses of the respective stems, they are used in various other ways, particularly the i stem – for example 読み物 yomi-mono "reading material"; compare 食べ物 tabe-mono "food" for vowel stem.

By contrast, vowel stem verbs have a single stem form, ending either in i or e, accordingly as -iru or -eru. These are referred to respectively as 上一段 kami ichi-dan "upper one-row" and 下一段 shimo ichin-dan "lower one-row", due to i being above e in the aiueo vowel ordering. In full terminology, the column of the final kana is also listed. For 見る みる miru is of マ行上一段活用 ma-gyō kami ichidan katsuyō "ma-column upper one-row conjugation" type and has stem:

• 見 み mi-

while 食べる たべる taberu is of バ行下一段活用 ba-gyō shimo ichidan katsuyō "ba-column lower one-row conjugation" and has stem:

• 食べ たべ tabe-

In Japanese dictionaries, in the readings of conjugable words the stem and the inflectional suffix are separated by a dot (・), as in 赤い あか・い aka.i "red". This is used to distinguish verb type, with consonant stem verbs having only the last kana treated as suffix, while in vowel stem verbs the last two kana are treated as suffix. The column 行 of the conjugation form corresponds to the kana immediately after the dot. For example:

• 帰る かえ・る kae.ru "return" – consonant stem ラ行五段
• 変える か・える ka.eru "change" – vowel stem ア行下一段

Note that for one-row verbs with only two kana, the entire verb is treated as a suffix, and no dot is displayed, as it would appear before the word. For example:

• 要る い・る i.ru "need" – consonant stem ラ行五段
• 居る いる iru "be (animate)" – vowel stem ア行上一段

The terms "Group I", "Group II", and "Group III" are primarily used in Japanese language education, and may be notated as (I), (II), (III) next to a verb. Similarly, the terms "u verb" (う verb) and "ru verb" (る verb) are educational terms, and may be notated as （う） or （る）.