Number sets

There are various sets of numbers: natural numbers (N), integers (Z), rational (Q), real (R)...
In this page, you can see definitions and relations between them.
http://www.mathsisfun.com/sets/number-types.html

Do you know its symbols?
N: Natural: 1, 2, 3, 4, ...
Z: Integers: .... -3, -2, -1, 0, 1, 2, 3, ....
(Z is for the German "Zahlen", meaning numbers, because I is used for the set of imaginary numbers)
Q: Rational: -5/3, -6/3, 2/5, 7/3, 8/2....
(Q is for "quotient" because R is used for the set of real numbers)
R: Real: 1.5, -12.3, 99, √2, π, ...

There are other number sets: Imaginary (I) and Complex (C)