Before and after doing: trước khi / sau khi

Trước khi means "before" and sau khi means "after", followed by an action: trước khi ăn (before eating), sau khi tốt nghiệp (after graduating). Like khi, the phrase usually comes first, then a comma and the main sentence: Trước khi ngủ, tôi hay đọc sách. Before I go to sleep, I usually read.

The phrase can also come second: Rửa tay trước khi ăn nha. Wash your hands before you eat. The action can have its own person: Sau khi con đi học, mẹ đi chợ. After the kids leave for school, Mum goes to the market. When it's the same person in both parts, say it only once.

Before a noun or a time, leave out khi: trước bữa ăn (before the meal), sau Tết (after Tết), trước bảy giờ (before seven). An action takes khi; a thing or a time doesn't.

In speech, "after eating" is often ăn xong: Ăn xong mình đi. We'll go after we eat. And "after that, then" is sau đó: Tôi ăn sáng, sau đó đi làm.