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 vs 五段
How to identify
- Is a special class irregular verb 為る or 来る
- 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 comprehensive list:
- 居る (い.る) - to be
- 得る (え.る) - to get
- 出る (で.る) - to leave
- 見る (み.る) - to see
- 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