Question

Quick question. What does a Q with a line above it mean in math symbols?

Answer 1

Many things, depends on context and author.

Answer 2

For example, if Q was a complex number, it could mean the conjugate of Q.

Answer 3

Well, because of the question, I know its not the conjugate. Any idea what else it could mean? In this question, Q itself just means rational numbers.

Answer 4

Literally anything as that isn't standard notation. It could mean all positive rationals, for example. It could also mean all rationals except 0.

Answer 5

Ok. Thanks! :) I'll look into those.

Answer 6

If you want, take a photo of that section of the page and post it.

Answer 7

It's this?
\[ \bar{\mathbb{Q}} \]

Answer 8

Yes, that's the symbol.

Answer 9

This really does depend on context. That could be the topological closure of Q, which is the reals; or it could be algebraic closure, which is the complex numbers; or it could be something else.

A copy of the page you're reading will resolve this.