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$\begingroup$

$X\cup_f Y = (X\amalg Y)/\{f(A)\sim A\}$

This is the definition of adjunction space in Wikipedia. I wasn't able to understand some signs: $/$ and $\amalg$. What do they mean?

Thanks.

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    There is much more on adjunction spaces, including their homotopy type, in my book "Topology and Groupoids" available from amazon sites. See an MAA review here http://mathdl.maa.org/mathDL/19/?pa=reviews&sa=viewBook&bookId=694212012-09-17

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The question is solved as in the comments.