Again: verb + lại

Lại after a verb means "again", in the sense of doing something over: Anh nói lại được không? Could you say that again? Em phải viết lại bài này. I have to rewrite this essay. It works like "re-" in English: redo, rewrite, rebook.

With an object, lại usually goes straight after the verb, but you'll also hear it at the end: đọc lại bài and đọc bài lại both mean "read the text again".

Gọi lại is "call back": Lát em gọi lại cho anh nha. I'll call you back in a bit. To ask someone to repeat something, Chị nói lại giùm em nha is warm and very Southern (in Hà Nội, giúp em … nhé).

For "over and over", say the verb twice, with đi after the first and lại after the second: Em nghe đi nghe lại bài hát này. I play this song over and over.

After verbs like "close" or "give back", lại doesn't mean "again": đóng cửa lại (close the door), trả lại (give back). And before a verb, lại adds surprise or annoyance, often meaning "again" (Em lại quên rồi. I've forgotten again) but not always: Sao em lại khóc? Why are you crying? Both are later patterns.