Circle with a line through...

Factual Questions
1

Yeah, that thingie…you see them on No Smoking signs all the time. Pretty much any kind of “No” anything signs. Red circle, bisected by a line 45% off vertical. My questiong, which shall surely reverberate through the halls of knowledge for decades to come…
What do you call that thing? No, really.

I’m writing a technical “how-to” guide, and while I shall be peppering it with pictures and such, I need to be able to tell people, “look for the icon with the circle-with-a-line-through-it over the top of it.” A bit awkward, to say the least. I’m sure it must have some sort of pseudo-intellectual kind of name, but I honestly have no clue where to start looking. Have you ever tried googling “circle with a line through it?”

Please help me, Obi-Wan…et. al.

You’re my only hope!
InkBlot
:eek:

P.S. Most of you will probably realize, “if you don’t know what word to use, how will any of your readers know what it means?” Truthfully, they probably won’t. So, they’ll come find me and ask. I’ll tell them, and I’ll have taught them something, even if it was against their will.

2

“Prohibited” circle?

3

After some googling, it seems to be called the “international symbol for prohibited”

???

4

It’s time to introduce you to the wonderful world of unicode:

http://www.unicode.org/charts/

The circle with a diagional line is shown on the page Misc. Math Symbols B.
Somewhere on the site, every symbol has a name, but it’s only descriptive. I can’t tell if they call it “circled reversed solidus” or "empty or reversed empty set.

5

The “empty set” symbol is different - it looks like a Ø, with the line protruding beyond the circle. It’s used in maths, and also resembles a letter in the Norwegian and Danish (I think) alphabets.

(Actually, in this font, they’re not the same. The empty set is a circle, not an O shape)

6

I’ve always just thought of it as the “no” sign. If somebody said, “Look for the symbol with the ‘No’ sign over it,” that’s what I’d look for.

7

It’s formally known as the International “No” Sign.

8

… and also International “No” Symbol.