Learn Hardcore Chinese: tā shuō zìjǐ shuìjiào de shíhou xǐhuan kāizhe kōngtiáo, bù shì yīnwèi wàimiàn hěn rè, érshì yīnwèi zhèyàng bǐjiào ānxīn. - She says that when she sleeps she likes to leave the air conditioner on not because it’s hot outside, but because that way she feels more at ease.

Emphasizes that it’s her own habit or preference.
Avoids possible ambiguity if the sentence were longer and had more people mentioned.
Sounds slightly more natural and smooth in Chinese in reported speech.

You could say 她说她睡觉的时候… and it would still be understandable, but 自己 is more idiomatic and clearly ties the action back to the speaker herself.

What is the function of 的时候 in 睡觉的时候? Is it like “when …” in English?

Yes. 的时候 (de shíhou) literally means “the time when …”, and in practice it works very much like English “when …”.

睡觉的时候 = “when (she) sleeps” / “when (she is) sleeping”
Structure: [verb / verb phrase] + 的时候 = “when (doing that verb)”

So 自己睡觉的时候喜欢开着空调 = “(she) likes to have the AC on when she sleeps.”

Why is it 开着空调 and not just 开空调 or 打开空调?

The key is the particle 着:

开空调 focuses on the action of turning on the AC (“turn on the AC”).
打开空调 also emphasizes the action (“switch on the AC”).
开着空调 uses 着, which marks a continuing state. It means “with the AC in the on state” or “having the AC on (and kept on)”.

In context:

睡觉的时候喜欢开着空调 = “(She) likes to sleep with the AC kept on.”
So 着 is used because the important idea is the ongoing state during sleep, not the moment of switching it on.

What exactly does 着 do grammatically in 开着?

着 (zhe) is an aspect particle that marks a continuous state resulting from an action.

Pattern:
Verb + 着 → “be in the state of having done that verb”

Examples:

开着灯 – “with the light on”
关着门 – “with the door closed”
穿着衣服 – “wearing clothes”

So 开着空调 means “with the air conditioner (in the state of) being on.” It describes the background state while something else (sleeping) happens.

Why is it 不是因为…，而是因为…? What does this pattern mean?

不是…，而是… is a very common contrast pattern:

不是 A，而是 B = “It’s not A, but rather B.”

When you insert 因为 after each part, you’re contrasting reasons:

不是因为 X，而是因为 Y
= “It’s not because of X, but rather because of Y.”

So in the sentence:

不是因为外面很热，而是因为这样比较安心
= “Not because it’s hot outside, but because this way she feels more at ease.”

Why is there 很 in 外面很热? Isn’t 热 itself already “hot”? Can you say 外面热?

In modern Mandarin, adjectives often need a degree adverb (like 很) when they function as predicates (i.e. when you say “A is adj”).

外面很热 is the default, natural way to say “it’s hot outside.”
Technically 外面热 is grammatically possible, but:
- It can sound abrupt or like part of a contrasting structure.
- On its own in daily speech it’s less natural and may feel like you’re comparing: “Outside (is) hot (as opposed to something else).”

Here 很 doesn’t always strongly mean “very”; it often behaves like a “linking adverb” that smooths “subject + adjective” → “subject is adjective.”

So 外面很热 is the normal, neutral predicate form.

What does 而是 add compared to just using 但是 or 可是?

而是 is used specifically in the fixed contrast pattern 不是 A，而是 B → “not A, but B.”
但是 / 可是 are more general “but / however” conjunctions that don’t inherently create a “not this, but that” correction.

Compare:

不是因为外面很热，而是因为这样比较安心。
Emphasizes: “The real reason is B, not A.”

If you tried:

因为外面很热，但是因为这样比较安心。
This is unnatural and unclear; you’d be saying “because it’s hot, but because this way is more reassuring,” which doesn’t work logically.

So 而是 is exactly the right word when you want to reject one explanation and replace it with the true one.

What does 比较 mean in 这样比较安心? Is it really “compare”?

Here 比较 (bǐjiào) is not literally “to compare”; it works as an adverb meaning:

“relatively / rather / somewhat / more (in comparison)”.

In casual speech, 比较 + adjective is often a softener:

这样比较安心 ≈ “this way is more reassuring / feels safer / feels relatively more at ease.”

Nuance:

It doesn’t specify compared to what explicitly (though context gives the contrast: with AC vs. without AC).
It makes the statement sound less absolute and more mild: not “this is the safest way ever,” but “this way makes me feel more at ease (than other ways).”

Is 安心 here an adjective (“safe, at ease”) or a verb (“to feel safe”)? How should I think of it?

In 这样比较安心, 安心 functions like an adjective meaning:

“feeling at ease / reassured / safe in one’s mind.”

You can treat 安心 as an adjective about your inner state:

我很安心。 – “I feel at ease.”
这样让我安心。 – “This makes me feel at ease.”

So 这样比较安心 = “This way is more安心 (more reassuring / more comforting).”

Why is there a comma before 不是因为? Does it mark a special structure?

Yes, the comma is marking the separation between:

The statement of her habit:
- 她说自己睡觉的时候喜欢开着空调，
The explanation and contrast of reasons:
- 不是因为外面很热，而是因为这样比较安心。

In spoken Chinese, this would correspond to a natural pause before the explanation of why. Commas in Chinese often separate clauses / ideas, not just complete sentences in the Western sense.

If the subject is 她说, why don’t we repeat 她 later in the sentence? For example, why not 而是因为她这样比较安心?

Chinese tends to drop pronouns when the subject is already clear from context.

After we say 她说, everything that follows is understood to be what she said and about her unless otherwise specified.

So we don’t need to say 她这样比较安心; 这样比较安心 is automatically understood as “this way (makes her) feel more at ease”.

You can say 而是因为她这样比较安心, and it’s grammatically fine, but it’s usually unnecessary and more wordy than native speakers prefer.

Could the sentence use 因为…所以… instead of 不是因为…而是因为…?

Not in the same way.

因为…所以… = “because … therefore …” (cause → result).
不是因为…而是因为… = “not because … but because …” (contrasting reasons).

If you changed it to 因为…所以…, you’d lose the contrast:

因为这样比较安心，所以她睡觉的时候喜欢开着空调。
= “Because this way she feels more at ease, she likes to sleep with the AC on.”

This is fine Chinese, but it only states the true reason; it no longer explicitly says it’s not because it’s hot outside. So it changes the nuance.

Are there any tone sandhi issues in this sentence I should watch for when speaking?

Yes, a few common ones:

不 before a 4th-tone syllable changes to a 2nd tone:
- 不是 is pronounced bú shì, not bù shì.
很 is 3rd tone, and in 很热 (hěn rè):
- When a 3rd tone is followed by a 4th tone, the 3rd tone often becomes a half-3rd tone (low dipping), so it sounds like a short low hěn then rè.
比较 (bǐjiào):
- 比 (bǐ) is a clear 3rd tone.
- 较 (jiào) is 4th tone. Again, 3rd + 4th: the bǐ tends to be low then down, not a full long dip.

Practically, the most important to remember explicitly is 不是 → bú shì. The others will become more natural with listening and practice.