Learn Hardcore Chinese: xiànzài hěnduō chéngshì de kōngqì wūrǎn hěn yánzhòng. - Nowadays, air pollution in many cities is very serious.

现在 is a time word meaning "now / nowadays". In Chinese, time expressions usually come before the subject or right at the beginning of the sentence.

Original:
现在很多城市的空气污染很严重。
"Nowadays, the air pollution in many cities is very serious."

You can:

Omit 现在 if context already makes the time clear:
很多城市的空气污染很严重。
This still sounds natural; it just doesn’t explicitly emphasize "nowadays."
Move 现在 inside the subject (less common but possible):
很多城市现在的空气污染很严重。
This sounds like "the air pollution in many cities now is very serious" – slightly more contrastive, as if you’re comparing "now" vs "before."

Putting 现在 at the very beginning is the most neutral and common way to set the time frame for the whole sentence.

What does 的 do in 很多城市的空气污染?

的 links a modifier to a noun, forming an "of / ’s" relationship.

很多城市的空气污染
= "many cities’ air pollution" / "the air pollution of many cities"

Structure:

很多城市 = "many cities" (modifier)
的 = possessive / attributive marker
空气污染 = "air pollution" (head noun)

So X 的 Y often corresponds to "Y of X" or "X’s Y" in English:

老师的书 = "the teacher’s book"
上海的天气 = "Shanghai’s weather"
很多城市的空气污染 = "many cities’ air pollution"

Why is there no measure word between 很多 and 城市?

You often see:

很多 + noun
as a fixed pattern: "many + [plural idea]"

So 很多城市 is natural and common.

In Chinese, a measure word is needed when there’s a specific number:

三座城市 (three cities)
五个城市 (five cities)

With 很多, you're expressing an indefinite, general "many", so you can usually put it directly before a noun without a measure word:

很多人 (many people)
很多学生 (many students)
很多城市 (many cities)

You can insert a measure word for emphasis or style:

很多个城市, 很多座城市

but that slightly emphasizes counting or is more specific; 很多城市 is the default, neutral form.

Why don’t we say 城市们 to show the plural, like adding -s in English?

In Chinese, nouns usually don’t change form for singular vs plural. Plural is understood from context or from words like 很多 ("many").

城市 can mean "city" or "cities" depending on context.
很多城市 clearly means "many cities" without needing 城市们.

The suffix 们 is used mainly with people or pronouns:

我 → 我们 (I → we)
他 → 他们 (he → they)
学生 → 学生们 (students — more emphatic/plural)

Using 城市们 is almost always unnatural in standard Mandarin.

Why isn’t there a 是 before 很严重? Why not 空气污染是很严重?

In Chinese, when an adjective is used as a predicate, you usually don’t use 是 before it.

空气污染很严重。 (correct, natural)
空气污染是很严重。 (possible but sounds marked/emphatic)

Basic rule:

Noun + 是 + noun
e.g. 他是老师。 (He is a teacher.)
Noun + (degree adverb like 很) + adjective
e.g. 天气很好。 (The weather is good.)

So:

空气污染很严重。
"The air pollution is (very) serious."

Adding 是 here can sound like stressing or contrasting:

空气污染是很严重，但是……
"The air pollution is very serious, but…"

For a simple descriptive statement, you leave 是 out.

Does 很 in 很严重 really mean "very" here? Or is it just a grammatical filler?

很 (hěn) is a degree adverb meaning "very," but in everyday sentences with adjectives, it often works more like a default linker to the adjective and may not feel as strong as "very" in English.

空气污染严重。
This can sound like a comparison ("the air pollution is serious (as opposed to something else)") or like a more abrupt, written style.
空气污染很严重。
This is the natural, neutral way to say "the air pollution is serious." Depending on context, it can be "is serious" or "is very serious."

So:

Grammatically, 很 is needed in many adjective predicates to make the sentence sound smooth and non‑comparative.
Semantically, it can mean anything from neutral "is serious" to genuinely "very serious", depending on emphasis and context.

What is the difference between 严重 and using something like 大 (e.g. 空气污染很大)?

Both 严重 and 大 can talk about how "bad" or "severe" something is, but they are used differently.

严重 (yánzhòng) = "serious, severe"
Used for negative problems, illnesses, dangers, etc.
- 问题很严重。 – The problem is serious.
- 污染很严重。 – The pollution is serious/severe.
- 病情很严重。 – The illness is serious.
大 (dà) = "big, large, great (in degree)"
With abstract nouns, 大 can mean "great degree / large amount":
- 压力很大。 – The pressure is great.
- 影响很大。 – The influence is big.
- 风险很大。 – The risk is great.

For 污染, 很严重 is the most natural way to say "very serious/severe". 污染很大 is not wrong but is less idiomatic; you’re more likely to see:

污染很严重。 (most common)
污染很大 in some contexts, but it can feel more like "a large amount of pollution" than "severe pollution" and is less standard in careful speech.

Is 污染 here a noun ("pollution") or a verb ("to pollute")?

In 空气污染很严重, 污染 is being used as a noun meaning "pollution."

Structure:

空气污染 = "air pollution" (compound noun)
很严重 = predicate, describing how serious that pollution is

If 污染 were used as a verb, you’d see patterns like:

工厂污染了河水。
"The factories polluted the river."

Here, 空气污染 functions as a thing (noun), not an action (verb).

Why is it 很多城市的空气污染 and not 很多城市里(的)空气污染? What’s the difference?

Both are possible, but the nuance is a bit different.

很多城市的空气污染
Literally: "many cities’ air pollution"
This treats 空气污染 as something those cities have (a property of the cities).
很多城市里(的)空气污染
Literally: "the air pollution in many cities"
The 里 emphasizes location ("inside / in").

In meaning, they’re very close, and in this sentence, 很多城市的空气污染 is more common and smooth. If you say 很多城市里, you’re putting a bit more focus on in those places rather than "those cities’ pollution as a characteristic."

Could we change the order inside 很多城市的空气污染 to something like 很多城市空气的污染?

很多城市的空气污染 is the natural, standard order:

很多城市的 → modifies
空气污染 → head noun

If you say 很多城市空气的污染, it sounds awkward and unnatural. Chinese avoids stacking 的 in this kind of rearrangement when there’s a clear, simple pattern available.

Think of it as nested like this:

(很多城市)的
- (空气污染)
  = the 空气污染 that belongs to 很多城市

Changing the order breaks that clear structure and confuses which part is modifying which.

How would you negate this sentence?

To negate the sentence, you usually put 不 before the adjective:

现在很多城市的空气污染不严重。
"Nowadays the air pollution in many cities is not serious."

If you want to sound softer or less absolute, you can say:

现在很多城市的空气污染不太严重。
"The air pollution in many cities nowadays is not too serious / not very serious."

How would you turn this into a yes–no question?

Two common ways:

Add 吗 at the end:
- 现在很多城市的空气污染很严重吗？
  "Is the air pollution in many cities very serious nowadays?"
Use an A‑不‑A pattern with the adjective:
- 现在很多城市的空气污染严重不严重？
  Literally: "Is the air pollution in many cities serious‑not‑serious nowadays?"

Both are natural; …很严重吗？ is more neutral and slightly more formal, while 严重不严重？ feels a bit more conversational.