Learn Hardcore Chinese: tā wǎnshang hěn wǎn cái shuìjiào.

It signals “not until,” with a sense of delay or later-than-expected timing. So “他晚上很晚才睡觉” means “He doesn’t go to sleep until very late at night.” 才 itself doesn’t mark past tense; it’s about timing relative to expectation.

Why is 很 before 晚? Can I say 他晚上晚才睡觉?

Many stative adjectives (like 晚 “late”) normally take a degree word when used adverbially. 很晚 is the natural way to say “very late.” “他晚上晚才睡觉” sounds off. Alternatives: 这么/那么/特别/非常晚, or use a specific time: 他晚上两点才睡觉.

Where does 才 go? Can I put it after the verb?

Structure: Subject + time phrase + degree/time phrase + 才 + verb phrase. Example: 他晚上很晚才睡觉. Don’t place 才 after the verb, and don’t say 他晚上才很晚睡觉. 才 must come before the verb/VP it scopes over.

Can I move 晚上 around? Can it go at the end?

Time words usually go before the verb. Acceptable: 他晚上很晚才睡觉; 晚上他很晚才睡觉. Putting 晚上 at the end (他很晚才睡觉晚上) is unnatural.

Is this sentence habitual or about one specific night?

It’s neutral; context decides. To make it about a specific past night: 他昨天晚上很晚才睡觉. To show a habit, add adverbs like 都/常常/经常/总是: 他晚上都很晚才睡觉 (He always goes to bed very late).

What’s the difference between 才 and 就?

才: later than expected; “not until.” 他凌晨两点才睡觉 (not until 2 a.m.).
就: earlier/sooner/easily; “as early as.” 他晚上九点就睡觉 (as early as 9 p.m.). Neither word is inherently “late/early”; both are relative to expectation.

How do I include a specific time with 才?

Place the time before 才:

他凌晨两点才睡觉 (He didn’t sleep until 2 a.m.).
他十二点半才睡 (He didn’t sleep until 12:30).
Add a day for clarity: 他昨晚一点才睡.

Pronunciation tips: any tone sandhi or pitfalls here?

晚上 is usually wǎnshang (neutral tone on 上). Some say wǎnshàng; neutral is common in colloquial speech.
很晚 is 3rd + 3rd; in speech the first becomes rising: hén wǎn.
睡觉 is shuì jiào (both 4th). 觉 here is jiào (not jué as in 觉得 juéde).
才 is cái (2nd).

Isn’t using both 晚上 and 很晚 redundant?

No. 晚上 sets the general time frame (at night), while 很晚 says how late within that frame. English does the same: “At night, he goes to bed very late.”

Can I use 睡 instead of 睡觉?

Yes: 他晚上很晚才睡 is fine. When describing degree/result with 得, use 睡: 他晚上睡得很晚. You normally don’t say “睡觉得很晚”; prefer 睡得很晚 or keep 才: 很晚才睡觉.

How do I say “He didn’t fall asleep until very late”?

Use 睡着 (shuì zháo, “to fall asleep”): 他晚上很晚才睡着.

很晚才睡觉: didn’t go to bed/start sleeping until late.
很晚才睡着: didn’t fall asleep until late (focus on the moment of falling asleep).

How do I say “He goes to bed too late”?

Use 太…了 or a habitual adverb:

他晚上睡得太晚了 (too late).
他晚上总是很晚才睡觉 (always very late).

Is 才 always “only”?

It has two common uses:

Timing: 才 + VP = “not until” (this sentence).
Small quantity: 才 + number = “only/merely” (他才五岁 “He’s only five”). Context tells which meaning.

Can I highlight the time with 是…的?

Yes, for a specific past event: 他是昨天晚上很晚才睡觉的. The 是…的 frame emphasizes when/how something happened.

Are there synonyms for 晚上? Do they change the nuance?

夜里: late at night (often later than 晚上).
深夜: deep into the night; more formal/literary.
晚间: formal for evening/night. Example: 他夜里很晚才睡觉 emphasizes the late-night feel.

Should I use 地 or 得 here, like 很晚地睡觉 or 睡觉得很晚?

No. 很晚地睡觉 is unidiomatic. Use either:

很晚才睡(觉) to emphasize “not until,” or
睡得很晚 to describe the degree/result with 得.