Verbs & aspect 动词与动态助词（了、过、着、在）

A precision trap. ✗ 我每天去了学校 (a daily HABIT takes no 了) → ✓ 我每天去学校。(Wǒ měi tiān qù xuéxiào.) — I go to school every day. ✓ 我以前常常去图书馆 (a past habit — still no 了). ✓ 我昨天去了图书馆。(Wǒ zuótiān qù le túshūguǎn.) — I went yesterday (one completed event). Decide first: a single completed action (了), a repeated habit (no 了, with 常常/每天/以前), or an experience (过)?

Both look back but differ. 过 (guo) = HAVE YOU EVER, an experience at some time: 我吃过北京烤鸭。(Wǒ chī guo Běijīng kǎoyā.) 了 (le) = a SPECIFIC completed event, often with a time: 我昨天吃了烤鸭。(Wǒ zuótiān chī le kǎoyā.) ✗ 你去了中国吗？(if you mean ever) → ✓ 你去过中国吗？(Nǐ qù guo Zhōngguó ma?) — Have you ever been to China? Negatives differ: 没吃过 (never eaten) vs 没吃 (did not eat). Never 没……了.

All three are pronounced "de" but do different jobs. 的 links a describer to a NOUN: 我的书 (wǒ de shū, my book). 地 makes an ADVERB before a verb: 他认真地学习。(Tā rènzhēn de xuéxí.) — He studies conscientiously. 得 introduces a MANNER complement AFTER a verb: 他跑得很快。(Tā pǎo de hěn kuài.) — He runs very fast. ✗ 他跑的很快 → ✓ 他跑得很快. Test: + noun 的; + verb 地; verb + how-well 得.

A negated action drops 了: 没 (méi) already says the event did NOT happen, so 了 (which marks that it DID complete) cannot sit with it. ✗ 我没吃饭了 → ✓ 我没吃饭。(Wǒ méi chī fàn.) — I have not eaten. ✗ 我昨天没去了 → ✓ 我昨天没去。(Wǒ zuótiān méi qù.) — I did not go yesterday. For a past experience that did NOT happen, use 没……过: 我没去过日本。(Wǒ méi qù guo Rìběn.) — I have never been to Japan.

Both describe something continuing, from different angles. 在 / 正在 = the action HAPPENING now: 他在开门。(Tā zài kāi mén.) — He is opening the door. 着 = the STATE left afterwards: 门开着。(Mén kāi zhe.) — The door is (standing) open. Another state: 墙上挂着一张地图。(Qiáng shàng guà zhe yì zhāng dìtú.) — A map is hanging on the wall. Ask: the doing (在) or the result that stays (着)?

了 (le) marks COMPLETION or a CHANGE OF STATE — not a past tense. A change in the PRESENT still takes 了: 天气冷了。(Tiānqì lěng le.) — The weather has turned cold. A PAST habit takes NO 了: 我小时候常常去外婆家 (I often went to grandma''s). ✗ 我每天去了公园 → ✓ 我每天去公园. For an experience use 过 (我去过日本); in progress use 在 (我在吃饭). Match the marker to the ASPECT, not the English tense.

是 (shì) links two NOUNS (X is Y); it is NOT used before a plain adjective. English "I am tall" uses "am", but Chinese uses a degree adverb, usually 很 (hěn), and no 是: ✗ 我是高 → ✓ 我很高。(Wǒ hěn gāo.) The 很 is just a link word and need not mean very. Use 是 only with a noun: 我是英国人；今天是星期一。For WHERE something is, use 在 (zài): 我的书在桌子上。(Wǒ de shū zài zhuōzi shàng.)