I need an way to remember the set operations very easily.

Does anybody have any idea?

For example, how do you remember the distinction between Set-Intersection and Set-difference? I regularly mess it up.

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    Do as many questions in your book as you have time for. – parsiad Apr 11 '15 at 15:23
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    Union is marked by a symbol resembling a u, and union starts with u, so that one's easy. Then intersection is the opposite of a union (sort of), and the symbol is the upside down union, so that's not too hard. Which other operations do you want? – 5xum Apr 11 '15 at 15:24
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    How do you remember the difference between **V** and **U**? They are so similar! Or between **p,q,b,d**? Or whatever letters which are similar in your native language. – Asaf Karagila Apr 11 '15 at 15:42

2 Answers2


As 5xum mentioned in the comments, union starts with a u and has a symbol $\cup$ that looks very much like a $u$. Then intersection is simply the same symbol flipped $\cap$.

As for what they mean, you can think of union $A \cup B$ as a cup (indeed, the LaTeX command for it is \cup) in which you pour all of the elements of both $A$ and $B$, whereas $A \cap B$ has two legs, one in $A$ and one in $B$, so it contains only those elements that are in both $A$ and $B$.

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The trick I used to memorize them actually stemmed from formal logic (which you may or may not have had any exposure to):

The symbol $\land$ is a way to symbolize the binary connective "and". Notice it looks like a "pointy" $\cap$. Similarly $\lor$ (or) looks similar to $\cup$.

Now, $$x\in A\cap B$$ can be read as $$x\text{ is in } A \textbf{ and } B$$ and $$x\in A\cup B$$ is $$x\text{ is in } A \textbf{ or } B$$

This might actually be why the symbols look similar, actually.

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