Learn Hardcore Chinese: mǎi xīn yóuxìjī de shíhou, tā xiān rènzhēn kàn wán le shuōmíng. - When buying a new game console, he first carefully read the instructions.

English generally repeats the subject (When he bought..., he...), but Chinese often doesn’t, to avoid redundancy. The listener understands that the he in both parts is the same person.

What exactly does 买新游戏机的时候 mean structurally? What is the role of 的 in 的时候?

买新游戏机的时候 is a time phrase meaning “when buying a new game console / when he bought a new game console.”

Structurally:

买新游戏机 – verb phrase: to buy a new game console
的 – turns the verb phrase into something that can modify a noun (like adding -ing or -time of ~ idea)
时候 – time; moment; when

So literally, 买新游戏机的时候 = the time of buying a new game console → when (he) bought a new game console.

的 here is a linker that lets a verb phrase (买新游戏机) modify a noun (时候).

Could I say 在买新游戏机的时候 instead? What’s the difference?

Yes, 在买新游戏机的时候，他先认真看完了说明。 is also grammatically correct.

Nuance:

买新游戏机的时候 – very common, neutral.
在买新游戏机的时候 – adds a bit more emphasis on “during the time when he was buying,” slightly highlighting the process or duration.

In everyday speech, people usually drop 在 and just say V 的时候. So the original sentence is the most natural.

Why use 时候 instead of just 时? Can I say 买新游戏机时，他先认真看完了说明?

You can say 买新游戏机时，他先认真看完了说明, and it’s grammatically correct, but:

时候 is more colloquial and common in everyday speech.
时 is shorter, a bit more formal or written in feel.

So:

Spoken / neutral: 买新游戏机的时候，他先认真看完了说明。
Slightly more formal / written: 买新游戏机时，他先认真看完了说明。

Meaning is basically the same.

What does 先 do here? Why is it placed before 认真 and 看完了?

先 (xiān) means “first; beforehand; before doing something else.”

In 他先认真看完了说明:

他 – he
先 – first
认真 – carefully / seriously
看完了 – finished reading
说明 – the instructions

So 先 tells you this action happens before some other action (for example, before he plays the game, although that second action is not stated).

Word order:

Adverbs like 先 usually come right after the subject, before the main verb:
- 他先看……
- 他先认真看完了说明。

You normally wouldn’t say 他认真先看完了说明; that sounds awkward. The natural pattern is:

Subject + 先 + (manner adverb like 认真) + Verb + …

Is 认真 an adjective or an adverb here? Why not 认真地看完了说明?

认真 (rènzhēn) is originally an adjective (serious), but in modern Chinese it’s very commonly used adverbially to mean “seriously; carefully; conscientiously”.

In spoken and informal written Chinese, you can often drop 地 when using adjectives as adverbs, especially with common words like:

认真 – carefully
慢慢 – slowly
清楚 – clearly (in some uses)

So:

他先认真看完了说明。 – very natural, everyday speech.
他先认真地看完了说明。 – also correct, sounds a bit more “written” or slightly more formal/explicit.

Both mean: He first carefully finished reading the instructions.

What is the exact function of 完 and 了 in 看完了? Why do we need both?

In 看完了, 完 and 了 are two different things:

完 (wán) – a resultative complement, meaning “to finish; to complete.”
- 看完 = to finish reading / to read to the end
了 (le) – an aspect particle (here attached to the verb phrase) marking the action as completed in time.

So structurally:

看 – read
看完 – read to completion (focuses on result)
看完了 – action of “reading to completion” is actually completed (past/complete event in this context)

If you said:

看完说明 – “(he) finishes reading the instructions” (can be more neutral about time, could be used in instructions or a sequence)
看完了说明 – clearly a completed event, often in a narrative past.

Both are possible in different contexts, but in a story describing what he did, 看完了说明 is very natural.

Why is 说明 at the end? Could I say 他先认真把说明看完了 instead?

Chinese normally places the object after the verb phrase, so:

看完了说明 = “finished reading the instructions”

This is a standard pattern: Verb + Result + 了 + Object.

You can also use the 把 construction:

他先认真把说明看完了。

This is also correct and common. Differences:

他先认真看完了说明。
- More neutral word order, slightly more compact.
- Focus on the action “finished reading” and then mentions what was read.
他先认真把说明看完了。
- 把 highlights the object (说明) and its resulting change (from unread to read).
- Slightly emphasizes doing something to the instructions and completing it.

Both are natural. The original sentence is perfectly fine and very typical.

Why is there no measure word before 说明? Should it be 一本说明书 or something like that?

说明 (shuōmíng) here means “instructions; manual; explanatory text.” It can be used:

As an uncountable-like noun, similar to “instructions” or “explanation” in English. Then no measure word is needed:
- 看说明 – read the instructions
- 看完了说明 – finished reading the instructions

If you want to emphasize the physical booklet, you can say:

说明书 (shuōmíngshū) – instruction manual/booklet
- 看说明书 – read the manual
- 一本说明书 – one instruction manual

So the sentence could also be:

买新游戏机的时候，他先认真看完了说明书。

But using 说明 alone is natural and normal in context; it treats “instructions” as non-countable text.

Could we drop 了 and say 他先认真看完说明? What would change?

Yes, 他先认真看完说明 is grammatically possible, but there’s a nuance:

看完了说明 – more clearly a completed event in the past (narrative, recounting what actually happened).
看完说明 – can sound a bit more general / instructional / sequential, like in steps:
- 先认真看完说明，再开始玩。
  First carefully finish reading the instructions, then start playing.

In the original sentence, which is telling us what he did, 了 makes it sound like a specific completed action. Without 了, it could sound more like a description of his habit or a general procedure, depending on context.

How do we know this sentence is in the past? There’s no “past tense” like in English.

Chinese doesn’t have tense in the same way English does; instead, it uses aspect markers and context.

In this sentence, clues for past/completed action are:

了 in 看完了 – signals completion of the action (perfective aspect).
The structure 买新游戏机的时候 – in many contexts naturally refers to a specific time in the past when he bought it (especially in a story or description).

So even without a “past tense” verb, the combination of 了 and the time phrase naturally makes the reader understand this as a past, completed event.