Talk:Beginner Japanese/Godan Verbs

I've read some other conjugations that confuses me. For example　（忘れる）:
 * 忘れなきゃ
 * 忘れず

More examples（歩く）：
 * 歩き
 * 歩か
 * 歩かす
 * 歩けぬ

Are they conjugations or irregularity?