# What does Z subscript + mean in sets

just for general knowledge what does Z subscript + mean in terms of set, i know Z is the set of integers but what does the subscript of "+" mean?

• Positive integers. – user61527 Jan 17 '14 at 7:45
• I have seen it some times refering to nonnegative integers, proof wiki identifies it as such proofwiki.org/wiki/Symbols:Z unlees it is a typo – clark Jan 17 '14 at 7:51

The $+$ in $\mathbb{Z}_+$ or sometimes written $\mathbb{Z}^+$ means the set of positive integers, rather than the typical set of all integers, $\mathbb{Z}$.

• Thank you! i know superscript + meant that but i wasn't sure subscript meant the same – L-V Jan 17 '14 at 7:48

$$\Bbb{Z}_+ = \Bbb{Z}_{>0} = \{ n \in \Bbb{Z} \mid n > 0 \}$$

For reals, $\mathbb{R}_+$ means the set of all positive real numbers, i.e. $(0, \infty)$. It seem s funny to me to do the same for integers since all positive itnegers are in $\mathbb{N}$, but I think that's what is meant.

• Some people have $0\in\Bbb N$, which means there is often ambiguity. – anon Jan 17 '14 at 7:50