TITLE: What does the sign $\propto$ mean?
QUESTION [29 upvotes]: I am a computer scientist, and one of my professors today used the symbol $\propto$. I tried to search that using google, but it returns no results, and I do not even know its name.
So, I would like to ask, what does the operator $\propto$ mean? What is its name, and how is it used?

REPLY [8 votes]: Since you say you're a computer scientist, it should be mentioned that Garey & Johnson use $A \propto B$ in their book Computers and Intractability – A guide to the Theory of NP-Completeness [1, page 34] to mean that there is a polynomial transformation from $A$ to $B$.
[1] Michael R Garey and David S Johnson. Computers and intractability, volume 174. Freeman
New York, 1979.