Explaination of which ... about

 First important thing:

👉 “Which … about” is not a fixed expression.
It depends on the sentence structure.

Let me explain clearly.

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🔹 1. “Which” = used for choices

We use which when there are limited options.

Example:

• Which book do you like?
• Which movie should we watch?

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🔹 2. “About” = shows topic

“About” means regarding / concerning.

Example:

• We talked about the problem.
• She asked about you.

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🔥 So what happens with “which … about”?

Usually, it appears in relative clauses like this:

Structure:

noun + which + subject + verb + about

Example:

• This is the topic which we talked about.
• That’s the movie which she told me about.

Here’s what’s happening:

• “which” connects the noun to extra information.
• “about” stays at the end because the verb needs it.

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🔎 Why is “about” at the end?

Because the verb requires it.

Example:

We say:

• talk about something
• think about something
• worry about something

So in a relative clause:

• the issue which we talked about
• the person which she worried about (better: who for people)

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🔥 Very Important

In modern English, we usually drop “which”:

Instead of:

• This is the topic which we talked about.

We say:

• This is the topic we talked about. ✅

Much more natural.

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🔹 For People → Use “who”

• She’s the person who I told you about.
• He’s the guy who we were talking about.

(Not “which” — use “who” for people.)

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🔥 Summary

Part	Function
Which	Connects extra info about a thing
About	Shows the topic (belongs to the verb)

So “which … about” isn’t one phrase — it’s just grammar happening together.