了 / 过 / 着 / 在 — the four aspects of Mandarin
Mandarin has no tense conjugation. Instead, it uses a small set of aspect particles that say WHEN-LIKE things about an action — whether it's completed, whether you've ever experienced it, whether a state is hanging on, whether you're in the middle of it right now. Lesson 11 introduced 了. This lesson lines up all four: 了 (two distinct uses — verbal le1 = completed; sentence-final le2 = change of state), 过 (experience: ever-in-your-life), 着 (durative state: hanging on), and 在 / 正在 + V (ongoing right now). Each one negates differently. Each one combines with the others differently. Getting this map straight is what moves you from A2 to B1.
了 the two-faced — completed action vs. change of state
There is really one character 了 but two grammatical jobs. Right after the verb (le1, wǒ chī le fàn) it marks the action as completed: 我吃了饭。 = I ate / I've eaten. At the very end of a clause (le2) it marks a change of state — 'now things are different': 下雨了。 = it's started raining; 我饿了。 = I'm hungry now; 她是老师了。 = she's a teacher now. Both can appear together: 我吃了三个苹果了。 = I've eaten three apples (so far / and that's where I am now). The verb-final 了 is grammatically attached to the verb; the clause-final 了 is attached to the whole sentence. Negation is asymmetric: completed 了 is negated with 没 and the 了 drops (我没吃饭 = I didn't eat). Change-of-state 了 is negated with 不...了 and the 了 stays (我不去了 = I'm not going anymore).
过 — 'ever, at some point, in your life'
过 guo (neutral tone) sits right after the verb and marks an experience the subject has had at some point. 我去过北京。 = I've been to Beijing. 我吃过中国菜。 = I've eaten Chinese food (before). 她学过日文。 = She has studied Japanese (at some point). Translate with English present perfect: 'have / has + ever'. Time depth doesn't matter — yesterday or twenty years ago, both work. Negation uses 没 and 过 STAYS: 我没去过北京。 = I've never been to Beijing. 我没吃过狗肉。 = I've never eaten dog meat. This is the key contrast with verb-final 了, where 没 makes 了 disappear. Question: V + 过 + 吗 or V + 过 + 没有: 你去过北京吗? / 你去过北京没有? = Have you ever been to Beijing? Frequency phrases sit AFTER 过: 我去过两次。 = I've been twice.
着 — durative state, the result hangs on
着 zhe (neutral tone) sits right after the verb and says the result of the action is currently in effect — a state is hanging on. The verb is usually a state-creating one: 开 (open), 关 (close), 坐 (sit), 站 (stand), 躺 (lie), 穿 (wear), 拿 (hold). 门开着。 = The door is open (it stays open, in that state). 她坐着。 = She is sitting (and remains sitting). 他穿着一件红衣服。 = He's wearing a red shirt. 桌子上放着一本书。 = There's a book lying on the table. The action ALREADY HAPPENED (someone opened the door, she sat down) — 着 says the resulting state continues. A second very common use: V1 着 + V2 chains a manner verb to the main verb: 她笑着说。 = She said with a smile (lit. smiling-ly said). 他站着吃饭。 = He eats standing up. Negation: 没V着 is rare; native speakers usually say 门没开 (the door isn't open) instead. Question: V着没有 / V着吗.
在 / 正在 + V — ongoing right now
To say 'is doing X right now', put 在 or 正在 BEFORE the verb. 我在吃饭。 = I'm eating (right now). 她正在看书。 = She is reading (at this moment). 正在 is a slightly more emphatic / formal version of 在 — both are common. You can also add a final 呢 for an extra colloquial 'right now' flavor: 我在吃饭呢。 = I'm eating right now (just so you know). The negation is the rarely-needed 没在 V or simply 没在 + V / 不在 V, but native speakers more often just answer with the negative perfective: 'Q: 你在吃饭吗? A: 没有 / 我没吃。' Question: 在 V 吗 / 在 V 呢吗: 你在吃饭吗? = Are you eating?
在 + V vs. V + 着 — the crucial split
Both 在 V and V 着 can translate as English '-ing', but they're aspectually different. 在 V = the action is IN PROGRESS (something is unfolding, happening dynamically). V 着 = a STATE persists (the result is steady, frozen). 她在穿衣服。 = She is putting on her clothes (action — getting dressed right now). 她穿着一件红衣服。 = She is wearing a red shirt (state — the wearing is steady). 他在开门。 = He's opening the door (the door is being opened — process). 门开着。 = The door is open (state — has been opened, stays open). 她在坐下。 is unusual — 坐下 is instantaneous. 她坐着。 = She is sitting (state). Rule of thumb: if you can replace English '-ing' with 'in the state of being', use 着. If you'd say 'in the middle of doing', use 在 V.
了 vs. 过 — completed once vs. ever-experienced
V 了 = a specific event was completed, usually with a definite occasion attached. V 过 = the subject has had this experience at some unanchored point in their life. 我去了北京。 = I went to Beijing (this trip / a specific time). 我去过北京。 = I've been to Beijing (in my life — could be once, twenty times, doesn't say when). 我吃了那个苹果。 = I ate that apple (a specific apple, finished). 我吃过苹果。 = I've eaten apples (have had the experience). Common test: if the natural English is 'I did X (then)' use 了. If it's 'I have ever / I've at some point' use 过. Negation flips the diagnostic: 没V (no 了) = didn't do this specific time. 没V过 (过 stays) = haven't ever done. 我没去北京。 = I didn't go to Beijing (this time). 我没去过北京。 = I've never been.
