Preface
I will be used a special kana-romaji mixed notation to differentiate between vowels which can be a part of a syllable with a consonant, and syllables which consist of only vowels. As an example:
- Ending with "う"
一段動詞 vs 五段動詞
How to identify
- Is a special class irregular verb 為る (する) or 来る (くる)
- Irregular verb
- Does not end with 〜る
- Godan verb
- Ends with 〜aる, 〜oる, or 〜uる
- Godan verb
After this set of conditions we're left with only verbs ending with 〜eる and 〜iる. At this point we cannot further determine which class does the verb belong to purely based on its reading. However, if we know some more facts about the verb, we can use some heuristics to help us with classifying the verb
Using the okurigana
- The verb has 3+ morae and the okurigana consists of only る
- Most likely a godan verb
- Examples: 遮る (さえぎ.る), 帰る (かえ.る)
- EXCEPTION: 出来る (でき.る) is ichidan
- The verb has 3+ morae and the okurigana consists of 2+ morae
- Most certainly an ichidan verb
- Examples: 起きる (お.きる), 変える (か.える)
If the verb has only 2 morae, this method cannot be used to determine the verb class. However, as there isn't many of 2-morae ichidan verbs, here's a list of all of them:
- 居る (い.る) - to be
- 得る, 獲る (え.る) - to get
- 出る (で.る) - to leave
- 見る, 観る, 看る (み.る) - to see, to watch, to look (after)
- 煮る (に.る) - to boil
- 寝る (ね.る) - to sleep
The less common ones are:
- 干る (ひ.る) - to dry
- 経る (へ.る) - to pass
Using the transitive verb pairs
If a verb has a transitive and intransitive variant, then the transitive variant ending with eru or iru is usually ichidan hajimeru is ichidan because there exists hajimaru akeru is ichidan because there exists aku ochiru is ichidan because there exists otosu
Exception: this will most likely not work for -u -asu verb pairs: chiru chirasu heru herasu
自動詞 vs 他動詞
他自動詞
他自動詞 are a special subtype of japanese verbs which can be used in both ways without changing its form. They are mostly suru-verbs, as they come from chinese, which historically didn't distinguish between transitive and intransitive verbs. There's also a small subset of native japanese verbs which belong to the hybrid transitivity class:
-
owaru - shiken ga owatta, sensei ga shiken wo owatta
How to identify
-
〜aる, 〜oる is always intransitive
- 始まる (はじ.まる) - to begin
- 上がる (あ.がる) - to rise
- 変わる (か.わる) - to change
- 起こる (お.こる) - to happen
-
〜aす, 〜oす is always transitive
- 溶かす (と.かす) - to melt (something)
- 落とす (お.とす) - to drop (something)
-
〜eる and 〜u can be either transitive or intransitive, when paired with 〜aす or 〜aる they will be the opposite type
- 始める (はじ.める) is transitive because 始まる (はじ.まる) is intransitive
- 溶ける (と.ける) is intransitive because 溶かす (と.かす) is transitive
- otherwise, one must learn which verb is which
- 開ける (あ.ける) is transitive and 開く (あ.く) is intransitive
- 切れる (き.れる) is intransitie and 切る (き.る) is transitive