An auxiliary verb attached to verbs to indicate past or completed action (the past/perfect auxiliary 'ta').
昨日、新しい映画を見た。
I watched a new movie yesterday.
宿題はもう終わったから、遊びに行っていいよ。
I've already finished my homework, so you can go out and play.
彼はそのことを聞いたことがあると言った。
He said he had heard about that before.
An auxiliary expressing a mild imperative or urging (used in literary or set expressions; limited usage in modern speech).