In short

Chinese builds relative time back-to-front: the reference event comes first and the time word comes last, so 吃饭以后 (chī fàn yǐhòu) = “after eating,” literally “eat-meal, after.” Use 以前 (yǐqián, before), 以后 (yǐhòu, after) and …的时候 (de shíhou, when / while) for relative time; 先…再/然后 (xiān … zài / ránhòu) to line up steps “first … then”; and 一边…一边 (yìbiān … yìbiān) for two things done at once.

The rule

Step 1 - Relative time words are postposed - the clause comes first. English says “before eating,” “after class,” “when I left.” Chinese reverses this: the event is stated, then the time word closes it. Think of 以前 / 以后 / 的时候 as tags stuck onto the end of a mini-clause.

[ Clause ] + 以前 / 以后 / 的时候

吃饭以前 (chī fàn yǐqián, before eating), 下课以后 (xiàkè yǐhòu, after class), 走的时候 (zǒu de shíhou, when leaving). The whole time phrase then normally sits at the front of the sentence, before the main clause: 下课以后，我们去吃饭 (Xiàkè yǐhòu, wǒmen qù chī fàn, after class we’ll go eat).

Step 2 - 以前 vs 以后 = before vs after. They also take number-spans: 三年以前 (sān nián yǐqián, three years ago), 两天以后 (liǎng tiān yǐhòu, two days later). Standing alone at the front of a sentence (not after a clause), 以前 means “formerly / in the past”: 以前我住在北京 (Yǐqián wǒ zhù zài Běijīng, I used to live in Beijing).

Step 3 - …的时候 = “when / while.” This frames a simultaneous background - something else is true at that same moment: 我走的时候，他还在睡觉 (Wǒ zǒu de shíhou, tā hái zài shuìjiào, when I left, he was still asleep). A verb-clause needs the linker 的 before 时候; never drop it.

Step 4 - Sequence: 先…再/然后 (“first … then”). For steps in order, mark the first with 先 (xiān) and the next with 再 (zài) or the connector 然后 (ránhòu). 先 and 再 are pre-verbal adverbs (after the subject, before the verb); 然后 is a conjunction that can open a fresh clause with its own subject:

Subject + 先 + V₁，(Subject) + 再 / 然后 + V₂

我们先吃饭，再看电影 (Wǒmen xiān chī fàn, zài kàn diànyǐng, we’ll eat first, then see a film). Here 再 means “the next step,” not “again” - that is a different sense of the same character (see Scope and time adverbs (就/才/再/又/还)). The second step can also be left unsaid, and then 先 alone means “first, before anything else”: 你先坐一会儿 (Nǐ xiān zuò yíhuìr, have a seat first), 我想先问一件事 (Wǒ xiǎng xiān wèn yí jiàn shì, I’d like to ask something first). The word order does not change - 先 is still the pre-verbal adverb of the pattern above.

Step 5 - Simultaneity: 一边…一边 (two actions at once). One subject doing two ongoing things at the same time:

Subject + 一边 + V₁ + 一边 + V₂

他一边吃饭，一边看电视 (Tā yìbiān chī fàn, yìbiān kàn diànshì, he eats while watching TV). Both actions belong to the same person. In casual speech it shortens to 边…边: 边走边说 (biān zǒu biān shuō, talk while walking).

Forms & patterns

The relative-time frame - clause first, tag last:

Sequence and simultaneity connectors:

Register variants of “before / after”:

Examples

Common mistakes

• 以前吃饭，我洗手。 -> 吃饭以前，我洗手。 (Chī fàn yǐqián, wǒ xǐ shǒu.) - The reference event comes before 以前/以后; the tag never leads its clause the way English “before” does. (Sentence-initial 以前 alone means “formerly,” a different meaning.)
• 我们吃饭先。 -> 我们先吃饭。 (Wǒmen xiān chī fàn.) - 先 is a pre-verbal adverb: after the subject, before the verb - never at the end like English “first.”
• 我们先吃饭，又看电影。 -> 我们先吃饭，再看电影。 (Wǒmen xiān chī fàn, zài kàn diànyǐng.) - In a planned sequence the “next” word is 再; 又 is “again, already happened” (lesson 23) and cannot open a future step.
• 他一边唱歌，她一边跳舞。 -> 他一边唱歌，一边跳舞。 (Tā yìbiān chàng gē, yìbiān tiào wǔ.) - 一边…一边 links two actions of the same subject; two different people cannot share it.
• 吃饭时候看电视 -> 吃饭的时候看电视 (chī fàn de shíhou kàn diànshì) - a verb-clause plus 时候 needs the linker 的; drop it and it is ungrammatical.

Tips

• Read the time words right-to-left. 以前/以后/的时候 are postpositions: state the event, then tag on “before / after / when.” 下课 + 以后 = “class-over, then-after.” This mirror image of English is the single thing to drill.
• In a sequence, 先 pairs with 再 or 然后, never 又. (On its own, with no second step stated, 先 needs no partner - see Step 4.) 再 = the next step (not “one more time”); if a new subject starts the second step, reach for the conjunction 然后 (or 然后再) instead of the bare adverb.
• 一边…一边 = one person, both at once. For two different people acting at the same time, don’t stretch it - use two clauses. In speech it clips to 边…边 (边走边说).
• Tone note on 一. In 一边 the 一 is yì (it precedes the 1st-tone 边), though alone it is yī; likewise 一起 is yìqǐ. Say the compound, not the citation tone.