trước vs sau — Before vs After in Vietnamese

Quick Answer

In Vietnamese, trước primarily means "before," "in front of," "ago," or "previous," while sau means "after," "behind," "later," or "next." Both words are highly versatile, functioning as adverbs, prepositions, or parts of conjunctions to indicate either spatial relationships (position) or temporal relationships (time/sequence).

Comparison Table

Detailed Explanation

Understanding trước and sau is fundamental for expressing location, time, and sequence in Vietnamese. While they are often direct opposites, their specific usage can vary with context.

Using trước

trước is used to indicate something that precedes in space, time, or order.

Spatial (In front of, Ahead): This refers to a physical position. It can be used as a preposition before a noun or as an adverb.

Example: Có một con mèo ngồi trước cửa. (There's a cat sitting in front of the door.)

Example: Bạn cứ đi trước đi. (You just go ahead.)

Temporal (Before, Ago, Earlier): This refers to time. It can function as an adverb or be part of a conjunction like trước khi.

Example: Chúng tôi ăn cơm trước khi đi học. (We eat rice before going to school.)

Example: Tôi đã đến Việt Nam hai năm trước. (I came to Vietnam two years ago.)

Ordinal/Sequence (Previous, First): This refers to an order or sequence of items or events.

Example: Bài học trước rất thú vị. (The previous lesson was very interesting.)

Example: Ai đến trước sẽ được chọn chỗ ngồi đẹp. (Whoever comes first will get to choose a good seat.)

Hán-Việt Connection: trước often corresponds to the Hán-Việt word tiền (前), meaning 'front' or 'before' (e.g., tiền sảnh - lobby, tiền sử - prehistoric).

Using sau

sau is used to indicate something that follows in space, time, or order.

Spatial (Behind, After): This refers to a physical position. It can be used as a preposition before a noun or as an adverb.

Example: Đừng đứng sau lưng tôi. (Don't stand behind my back.)

Example: Anh ấy chạy sau mọi người. (He ran behind everyone.)

Temporal (After, Later): This refers to time. It can function as an adverb or be part of a conjunction like sau khi.

Example: Tôi sẽ gọi cho bạn sau. (I will call you later.)

Example: Sau khi tan làm, tôi thường đi tập gym. (After finishing work, I often go to the gym.)

Ordinal/Sequence (Next, Following, Last): This refers to an order or sequence of items or events.

Example: Tuần sau tôi có kỳ thi. (Next week I have an exam.)

Example: Xin mời khách hàng số sau. (Next customer, please.)

Hán-Việt Connection: sau often corresponds to the Hán-Việt word hậu (後), meaning 'back' or 'after' (e.g., hậu quả - consequence, hậu vệ - defender).

Example Pairs

Common Patterns

trước khi + [clause]: before [doing something]

Example: Tôi luôn kiểm tra email trước khi bắt đầu làm việc. (I always check email before starting work.)

sau khi + [clause]: after [doing something]

Example: Sau khi ăn trưa, chúng tôi thường đi dạo. (After having lunch, we often go for a walk.)

[duration] trước: [duration] ago

Example: Tôi tốt nghiệp đại học năm năm trước. (I graduated from university five years ago.)

[duration] sau: [duration] later

Example: Một tuần sau, cô ấy đã trở về. (One week later, she returned.)

trước đây: in the past, previously

Example: Trước đây tôi sống ở thành phố Hồ Chí Minh. (Previously, I lived in Ho Chi Minh City.)

sau này: in the future, later on

Example: Hy vọng sau này chúng ta sẽ gặp lại. (Hope we will meet again later on.)

trước mặt: in front of one's face; openly, directly

Example: Anh ấy dám nói điều đó trước mặt tôi. (He dared to say that to my face.)

sau lưng: behind one's back; secretly, covertly

Example: Đừng nói xấu người khác sau lưng họ. (Don't badmouth others behind their back.)

ngay trước / ngay sau: just before / immediately after

Example: Anh ấy đến ngay trước tôi. (He arrived just before me.)

Example: Tôi sẽ gọi lại ngay sau cuộc họp này. (I will call back immediately after this meeting.)

trước đó / sau đó: before that / after that

Example: Bạn đã làm gì trước đó? (What did you do before that?)

Example: Ăn tối xong, sau đó chúng ta đi xem phim. (After dinner, then we go watch a movie.)

Common Mistakes

Mistake 1 — Using trước for 'next' or sau for 'previous' in sequence

Learners sometimes confuse trước and sau when referring to sequential items like chapters, pages, or turns.

❌ Tôi sẽ đọc cuốn sách trước. (Intended: I will read the next book.)

✅ Tôi sẽ đọc cuốn sách sau. (I will read the next/latter book.)

Why it's wrong and how to fix it: In an ordinal context, trước refers to something that precedes (e.g., the previous one, the one that came first), while sau refers to something that succeeds (e.g., the next one, the one that comes later). If you mean 'the next book' or 'the following book', you should use sau.

Mistake 2 — Incorrect placement with time expressions for "ago" or "later"

When expressing a duration of time relative to the present (e.g., "three years ago," "two days later"), trước and sau must follow the time duration.

❌ Trước ba năm tôi sống ở Hà Nội. (Intended: Three years ago I lived in Hanoi.)

✅ Ba năm trước tôi sống ở Hà Nội. (Three years ago I lived in Hanoi.)

Why it's wrong and how to fix it: The correct structure for expressing "X time ago" or "X time later" is [Time duration] + trước/sau. Placing trước or sau before the duration is incorrect.

Mistake 3 — Using trước instead of trước khi for a clause

When "before" introduces a clause (a phrase with a subject and a verb), you need the conjunction trước khi, not just trước.

❌ Tôi uống cà phê trước tôi đi làm. (Intended: I drink coffee before I go to work.)

✅ Tôi uống cà phê trước khi tôi đi làm. (I drink coffee before I go to work.)

Why it's wrong and how to fix it: trước alone acts as a preposition or adverb. To connect two clauses, you need the conjunction trước khi (or sau khi for "after"). Omitting khi makes the sentence grammatically incomplete when linking clauses.

Quick Quiz

Fill in the blank with trước or sau:

1. Bạn ngồi _____ tôi nhé, tôi không muốn ngồi cuối cùng.

Hint: The speaker wants someone to sit in front of them to avoid being the last.

2. Tôi sẽ gọi điện cho bạn _____ khi tôi đến nơi.

Hint: This refers to an event happening after another event.

3. Cuộc họp bắt đầu năm phút _____ rồi.

Hint: This refers to a duration of time in the past, relative to now.