Categories are important when conjugating Japanese verbs, since
conjugation patterns vary according to the verb's category. For example, and belong to different verb categories (quinquegrade and unigrade, respectively) and therefore follow different conjugation patterns. Most Japanese verbs are allocated into two categories: • • Statistically, there are about twice as many quinquegrade verbs than unigrade verbs.
Classical Japanese had more verb groups, such as and , which are archaic in
Modern Japanese. The word
grade in
quinquegrade and
unigrade is translated from . In grammar,
dan is a synonym for and opposite to . The translations for
dan/
retsu and
gyō vary, either of them can be translated as "row" or "column" depending on how the
gojūon table is laid out, but the distinction is simply that
gyō is named after consonants, as , while
dan/
retsu is named after vowels, as in or . The consists the kana , , , , , which differ only by vowels; while the consists of the kana , , , , , , , , , , , , , , , which differ only by consonants. The class consists of verbs whose inflection forms make use of all five grades, or five vowels. For example, the inflection forms of the verb are /, , , and . These verbs developed from the earlier class, after a historical sound change that turned such forms like into and resulted in an additional vowel (see
Late Middle Japanese). The class consists of verbs that occupy only one grade, or one vowel. Dictionaries may further divide this class into ) if the vowel is the "upper"
i, and ) if the vowel is the "lower"
e. The verb , whose inflection forms are , , and /, is an example of an "upper unigrade" verb, and the verb is a "lower unigrade" verb. Some unigrade verbs evolved from earlier forms of bigrade verbs ( (sometimes also known as ) and ). Dictionaries often list ancestral forms of modern verbs as well as their classes. While many authors use
bigrade and
quadrigrade consistently, they also use any combination of
unigrade,
monograde,
quinquegrade,
quinquigrade and
pentagrade. Some dispense with altogether and prefer only even for modern Japanese (see
Godan vs yodan below). Plain English alternatives to "unigrade", "bigrade", "quadrigrade" and "quinquegrade" include "
one-grade", "
two-grade", "
four-grade" and "
five-grade"; "
one row", "
two row" and "
four row"; "
one-step", "
two-step", "
four-step" and "
five-step"; or "
one-vowel", "
two-vowel" and "
four-vowel". Historically, the so-called verbs and were sometimes known as , given that their forms contain three out of the five vowels of Japanese. Here is a visualization that compares various verb conjugations to an extracted column of the
gojūon table. } In the table above, the verb uses kana from all
5 rows of the gojūon table in its inflectional suffix—, , , and —amongst its conjugations. Thus, it is classified as a "class-5" (or more formally "
quinquegrade") verb. Meanwhile, the verbs and each use kana from only
1 row of the gojūon table in their verb-stem's suffix— and respectively. Thus, they are classified as a "class-1" (or more formally "
unigrade") verbs.
Godan vs yodan All modern
godan verbs are derived from historical
yodan verbs. The distinction between these two classes relies solely on the interaction between the and the auxiliary (historically, ). Consider the verb : •
kaka- +
-mu →
kakamu (historical form) →
kakau (historical form) →
kakō (modern form) The shift of vowels from
au to
ō was regular and expansive during
Late Middle Japanese, and it practically introduced an additional to the inflectional forms of
yodan verbs: The term is a fairly modern coinage. During the time when
modern kana usage was being adopted to write in place of
historical kana usage, one of the changes concerned how such a form as
kakō should be spelt. The modern spelling was proposed along with
godan as the name for the modernized
yodan class. Traditionalist grammarians, on the other hand, would insist on such spelling as to reflect the historical pronunciation
kakau, and on the modern pronunciation being inferred from such spelling. Some argued that a single interaction with the auxiliary
u did not justify creating an entire new grammatical class, given that the
mizenkei does not involve a vowel shift with any other auxiliary: •
kaka- +
-nai →
kakanai •
kaka- +
-nu →
kakanu •
kaka- +
-n →
kakan •
kaka- +
-zu →
kakazu Moreover, the auxiliary
-ta and the particle
-te also notably alter the ''ren'yōkei'': •
kaki +
-ta/-te →
kaita/te •
omoi +
-ta/-te →
omotta/te •
yomi +
-ta/-te →
yonda/de Yet, such alterations are not reflected by either the term
yodan or the term
godan at all, despite occurring in both these supposedly different inflections (although in , these alterations in pronunciation must be inferred from the spellings). This means that exceptional interactions with auxiliaries and particles like these ought not to be the basis for naming verb classes. Obviously, the spelling reform took place and the term
godan became mainstream. Historical kana usage is now reserved only for the writing of classical Japanese, and
yodan verbs are largely considered a classical Japanese class while
godan verbs make up a fundamental part of modern Japanese.
Japanese language education Within
Japanese language education, various terminologies are used in lieu of the Japanese nomenclature for "quinquegrade" and "unigrade" verbs. In literature adopting the "Group I / II / III" terminology, the terms (I), (II) or (III) may be notated beside verbs. Similarly, (う) or (る) may be notated beside verbs in literature adopting the " / " terminology.
Consonant and vowel nomenclature The terms "consonant stem verbs" and "vowel stem verbs" come from a pattern that emerges from studying the actual structure of the words rather than the written representation. When considering the invariant part of the verb (the
verb stem), the final phoneme determines the classification of the verb group. If the verb stem's final phoneme: • is a consonant, then it is a
consonant stem verb (quinquegrade verb) • is a vowel, then it is a
vowel stem verb (unigrade verb) There are criticisms of the consonant and vowel nomenclature: • When quinquegrade verbs end with , the verb's invariant stem always ends with a vowel, yet is still classified as having a consonant stem. For example, has the vowel "
a" as the invariant suffix, yet it is still categorized as a "consonant stem verb". In these cases, this apparent expection is resolved by realizing that the verb's invariant stem ends in the consonant
w. The
w is normally suppressed, but surfaces in the negative form, as seen in . Traditionally these verbs ended in
-hu, which is still seen on occasion in
historical kana usage, and thus unambiguously ended in
h. • When godan verbs end with , the verb's invariant stem always ends with an "s" rather than a "t". Since the consonant stem terminology focuses on rōmaji, this could lead to conjugation errors. For example, in its negative conjugation does
not become as the consonant stem system might have one believe; the correct conjugation is . The matter is resolved when phonemic notation of "tu" used by
Kunrei-shiki romanization is applied instead. • In the case of the
past-tense and
te forms of conjugation, the 'invariant' stem changes such that the consonant is removed from all godan verbs (except verbs ending in or ). This means the defining characteristic of consonant stem verbs cannot be used to define consonant stem verbs for the past-tense or
te forms. The true "invariant stem", which is consistent amongst all conjugations, precedes the so-called "invariant consonant". ==Verb classification==