# What is this No thing?

What exactly is this No? Is there any other use of it other than graphs? Thank you so much. I am not trying to cram or anything it's just that I took a course online and a lot of the time it focused on concepts rather than notation. Sometimes when notation comes up I don't understand it.(seen in precal textbook)

• It seems to be literally the English word "no." As in, $g(8)$ doesn't exist. There is no $g(8)$. – Akiva Weinberger Aug 27 '15 at 3:25
• This No thing is Nothing. – vadim123 Aug 27 '15 at 3:27

I think the book is trying to tell you that $g$ is not defined at 8, by telling you that there's no value $g(8)$, showing with that vertical arrow where it would have been if it was defined.
• Ok that makes perfect sense. Thank you. I now see that there is a mention a few pages later that 8 is outside the domain of $g$. I just didn't put those two things together. – user253055 Aug 27 '15 at 3:31
• @AAron It's right at the top of the image actually. "$f(g(8))$ does not exists because 8 is outside..." But, yeah, it's not entirely obvious at first glance. – Graham Kemp Aug 27 '15 at 3:41