TITLE: What does $\mathbb Z_+$ mean?
QUESTION [5 upvotes]: I am not so sure whether the meaning of $$\mathbb Z_+$$ is very clear. How many different definitions are there? Does the definition that is used depend on whether the writer is English or German?
In French maths, this notation doesn't exist.

REPLY [5 votes]: Symbol "$+$" means "positive", so $\mathbb{Z}_+$ shoud properly be understood as $\{1,2,3,\ldots\}$. It's less confusing that undefined $\mathbb{N}$ in some paper, where we don't know if it includes $0$.