What is this sign above the letter?

Question

Discrete Math

Hello
What are the underscores above the letters? If this is a negation, but they look like this ¬ ?

Answer 1

If this is a negation, but they look like this ¬?

It also looks like this: "!". But that doesn't stop it from being negative. The "¬" before an expression is identical to the horizontal bar above the expression.