I'm using the amsmath package, and I want to put in a sentence, the not similar binary operator. I tried this:

... bla bla $ a \nsim b $ bla bla ...

I get the error:

"Undefined control sequence".

By the way, if I put \sim it works, but I want negate it.

  • 4
    Welcome to TeX.SX! You need \usepackage{amssymb}, which isn't automatically loaded by amsmath. – egreg Mar 10 '14 at 17:59
  • Hey thank you. Oh sorry i don't know this thing, i thought that all i need is inside amsmath. Noob question :) – optimusfrenk Mar 10 '14 at 18:09
  • See What does each AMS package do? – Werner Mar 10 '14 at 18:18
  • 1
    Please consider accepting answers that you consider best solved your problems. – Gonzalo Medina Jul 22 '14 at 16:53

The command \nsim is listed in table 69 of the Comprehensive LaTeX Symbol List, under the caption

AMS Negated Binary Relations

In section 1.1 of the document, we find

“AMS” means to use the AMS packages, viz. amssymb and/or amsmath.

Actually most of the symbols with that tag require amssymb and this is the case for \nsim.

enter image description here

Note that the result of \not\sim is rather different, so the final answer is


... bla bla bla $a \nsim b$ bla bls ...


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