# What does it mean "about which"?

I'm reading the definition of "axis" in oxford dictionary, and I see there this definition:

An imaginary straight line passing through the centre of a symmetrical solid, about which a plane figure can be conceived as rotating to generate the solid.

Can you please replace this two word with other once, since I don't understand their meaning?

Note, I generally understand the meaning of the sentence, but I don't understand the meaning of the idiom "about which".

• Around which( AmE) might be clear.
– V.V.
Commented Nov 7, 2015 at 14:45
• Thank you, but I really still not understand the meaning of this idiom. Commented Nov 7, 2015 at 14:59
• An axle is something about which a wheel rotates.
– user20792
Commented Nov 7, 2015 at 15:31
• You could rephrase this sentence (loosely) as "An axis is an imaginary straight line through the centre of a solid, and a plane figure rotates around it to generate the solid. Commented Nov 7, 2015 at 15:37

This is an example of the syntactic device called “pied piping”. In this, a relativizer (in this case which) standing for the object of a preposition in the following relative clause drags the preposition along with it to the front of the clause so that the syntactic roles are more clearly visible.

In your example, the relative clause headed by which is additional information about the line which can be represented as a ‘canonical’ independent clause:

To make this a relative clause modifying the noun phrase An imaginary straight line &c, we replace ‘the line’ with which and move that to the front of the clause:

But in a longish clause there is some danger that the reader may lose track of the relationship between which and about; the reader may see about to sitting together and read that as meaning “on the verge of”, which is pretty nonsensical. To prevent that sort of misparsing and ensure that the reader understands that which is the object of about, we “pied pipe” the preposition along with its object:

The term derives from a charming German story made famous in the English-speaking world by Browning’s The Pied Piper of Hamelin.

• the problem is that the OP does not understand the meaning of about in this context, and your answer is ridiculously too complicated for him or her.
– user20792
Commented Nov 7, 2015 at 17:13
• @User1 Are you sure? The suggestion that around could be substituted didn't help OP. It looks to me like OP has not grasped the syntactic relationships in this sort of relative clause. Commented Nov 7, 2015 at 17:17
• Thank you for your answer. I'm sorry if I didn't clear well. I understand the concept, but I have problem with the understanding of "about which" that for me it's not understood. It's very simple problem belonging to the meaning. I tried to check it on many dictionaries and I didn't find something about, and that's why I came here to ask my question. In any case, I re-vote your answer up, because it's not nice to vote your answer down. Commented Nov 7, 2015 at 18:23
• @Assiduous The important thing, is has somebody explained this for you? If not, we need to dig a little deeper and see where the problem lies. Commented Nov 7, 2015 at 18:39
• I'm sorry to say not, but this is the true. Commented Nov 7, 2015 at 18:50

If you place an imaginary line through the centre of a symmetrical solid and imagine that a plane (flat)figure is rotating around this line,this figure causes to exist the solid."solid"is a geometric figure having three dimensions.