Usage of ない Forms:

ない Form:

The part of the words underlined below is called the ない Form.

The vowel before -masu in the verbs of this group is always [i] and is replaced by [-a] to make it a ない Form.

Exceptions to this rule are かいます、Where the i is replaced by wa and such verbs as はなします＆まちます、Where shi and chi is replaced by sa & ta respectively.)