Negative Imperfective Form
As the name of the form suggests, this form is used for the negation of the habitual or future aspects of the verb.
How to derive the Negative Imperfective form:
- Group 1: Change the final る to ない
- Group 2: Change the final vowel u to a and add ない
- Group 3: くる→こない、する→しない
Exception: The negative imperfective form of the verb ある is ない.
Consider the single vowel u （う） at the end of certain verbs such as kau （かう） as having the hidden consonant w before the vowel u. In other words, the original form of kau （かう） is ka(w)u. This information is important when the last vowel u changes to a in the negative form before adding nai （ない）. The negative of kau （かう） therefore is kawanai （かわない） rather than kaanai （かあない）.
How to use the form:
When this verb is used in speech at the end of a sentence, it indicates casual speech. When used in writing, this form indicates that the writing is impersonal (such as newspaper articles, essays, journals, etc.).
'I don’t eat sushi.'
'I won't eat sushi.'