13

What does the symbol := mean in mathematics? for example, C(continuum) := |R|

Asaf Karagila
  • 393,674
  • 9
    It usually means that this is a definition, not a proven/provable statement or an equation where you are trying to solve something. – Thomas Andrews Jul 05 '16 at 18:53
  • @ThomasAndrews oh, thank you verymuch! –  Jul 05 '16 at 18:54
  • I could have sworn someone has asked this question before recently. I just can't find it right now. If someone can find where the duplicate is, that would be helpful. –  Jul 05 '16 at 18:58
  • @KingDuken, do you mean this http://math.stackexchange.com/questions/1838678/confused-about-notation-versus-plain-old – Zain Patel Jul 05 '16 at 19:09
  • Thanks @ZainPatel. That first link is what I was talking about. –  Jul 05 '16 at 19:10

1 Answers1

6

It means it is a definition in most contexts.

$f(x):=x^2-\sin 2x + \pi$ means I define $f(x)$ by the expression on the other side.

However, in most contexts, it is a superfluous notation as you argue around it.

Sumax
  • 212
Zelos Malum
  • 6,570
  • 1
    While I agree that it isn't necessary most of the time, I'd still encourage its use, because it provides some additional help to the reader. (E.g. in fine structure theory there is a huge amount of notation floating around and I welcome any kind of help to keep track of all of it - especially during talks.) – Stefan Mesken Jul 05 '16 at 19:43