By, with, in: bằng (transport, tool, language)

Bằng says how something is done: by which vehicle, with which tool, in which language. It goes after the verb, and after the thing acted on if there is one, right before the thing you use: Tôi trả bằng thẻ. I'll pay by card. Người Việt ăn cơm bằng đũa. Vietnamese people eat rice with chopsticks.

For a language, put tiếng before the country's name: nói bằng tiếng Anh (say it in English), viết bằng tiếng Việt (write it in Vietnamese).

To ask how, put gì where the answer goes: Em đi làm bằng gì? How do you get to work? The answer can repeat bằng: Bằng xe buýt. With transport, though, people often drop bằng and put the vehicle straight after đi: Em đi xe buýt. I take the bus.

English uses "with" for people and for tools alike, but Vietnamese doesn't. With a person, it's với: đi với bạn, go with a friend. With the thing you use, it's bằng. Bằng can also say what something is made of: bàn bằng gỗ, a wooden table. And in comparisons it means "as … as": Em cao bằng chị. I'm as tall as you.