Learn Hardcore Chinese: tā guān dēng le, tā guān mén le. - She turned off the light, and he closed the door.

It marks a new, changed situation or a completed event. In 她关灯了 and 他关门了, 了 tells us the actions have happened and the resulting state now holds (the light is off; the door is closed). Without 了, 她关灯 / 他关门 sounds habitual or instruction-like, not a one-time completed action.

Can I say 她关了灯 instead of 她关灯了? What’s the difference?

Both are correct, but the nuance differs:

她关灯了: sentence-final 了 highlights the new situation now.
她关了灯: verb-了 highlights completion of the action. In many contexts they’re interchangeable. You’ll also hear both combined in casual speech: 她关了灯了, though one 了 is usually enough in careful writing.

Would a 把-sentence be more natural with objects like 灯 and 门?

Very common and natural. Use 把 to foreground the affected object:

她把灯关了。
他把门关了。 把 is preferred when the object is specific/known and you want to stress the result on that object.

What’s the difference between 关, 关上, 关掉, and 关闭?

关: general close/turn off; the default.
关上: resultative; emphasizes ending up closed/shut (common with doors/windows): 关上门.
关掉: turn off/shut off (often lights/devices): 把灯关掉.
关闭: formal/literary or signage: 商店已关闭.

Is 他关门了 ambiguous? Could it mean a shop is closed?

Yes. 关门 also means “close for business.” Disambiguate with context:

He closed the door: 他把门关了。/ 他关上门了。
The shop is closed: 商店关门了。
He closed his shop: 他的店关门了。

How do I negate these sentences?

Use 没(有) for past/completed events and drop 了:

她没关灯。
他没关门。 To say “not yet,” use 还没(有):
她还没关灯。
他还没关门。 Don’t use 不 to negate completed past actions; 不关门了 means “(he) won’t close the door anymore,” a different meaning.

Where do adverbs like 已经 or 刚 go?

Place them before the verb phrase; 了 often still appears:

她已经关灯了。
他刚关门。/ 他刚关门了。 (both heard; 了 adds the “now it’s done” feel) Typical order: Time > manner/adverbs > place > subject’s verb phrase is also common in spoken Chinese flexibility.

Is the comma here functioning like “and”? Should I use 和?

The comma simply coordinates two clauses, much like “and.” You normally don’t use 和 to join whole clauses. If you want to make the link explicit:

Addition: 她关灯了，他也关门了。
Sequence: 她关灯了，然后他关门了。

What if the same person did both actions?

Use a single subject and link the verbs:

她关了灯又关了门。
她把灯和门都关了。
她先关灯，然后关门。

How do I describe the state vs the change of state?

Change of state (now closed/off): 门关了。/ 灯关了。
Ongoing state (is closed/off): 门关着。/ 灯是关着的。 着 marks a continuing state; for lights, 灯关着 is heard, though 灯是关着的 is a bit clearer.

Why is 了 at the end and not right after the verb?

Sentence-final 了 signals a new situation. When you put 了 right after the verb (关了灯), it’s the perfective 了 marking completion. Both are valid; they just emphasize slightly different things. Many sentences can take either, depending on focus.

Can I drop 了 in one clause but keep it in the other?

Better to be consistent if both actions are similarly completed. 她关灯，他关门了 sounds lopsided. Prefer:

她关灯了，他关门了。
她关了灯，他关了门。 Or add a time word that clearly sets the actions in the past.

Do 我 need measure words for 灯 and 门?

Only when specifying number or using a demonstrative:

一盏灯 (one lamp/light), 那盏灯
一扇门 (one door), 这扇门 Examples: 她关了那盏灯，他关了这扇门。

Can I omit the subjects in Chinese?

Yes, if context is clear:

关灯了，关门了。 Chinese often drops known subjects to sound natural and concise.

How are the pronouns pronounced and distinguished?

她 tā (she) and 他 tā (he) are both pronounced tā (first tone). The neuter 它 tā (it) is also tā. You tell them apart by character or context, not sound.

What are the pronunciations and tones here?

她 tā (1st), 关 guān (1st), 灯 dēng (1st), 了 le (neutral)
他 tā (1st), 关 guān (1st), 门 mén (2nd), 了 le (neutral)

Are the spaces in the sentence normal?

No. Standard Chinese writing has no spaces between words. The sentence is normally written as: 她关灯了，他关门了。 Spaces are added here only for learning/annotation.