# need help to enter the orthogonal sign, the upside down T.

I have search on Google and never came across any idea how to enter this damn sign. would anyone give me some hint?

You need UpTee:

UpTee[x, y]


or

x \[UpTee] y


or, using the input alias,

x ESC uT ESC y


x ⊥ y

• If you're simply trying to reproduce the character in text (any document type), a useful resource is Wikipedia's List of Unicode characters. Interestingly, that document lists it as UpTack (alternatively falsum), but not UpTee as @kglr comments. Irregardless, you can locate it visually in their Mathematical Operators subsection: en.wikipedia.org/wiki/… – flith Nov 3 '16 at 9:16
• UpTee?? But that's no fun. I've always wanted to say "There's the perp" – Daniel Lichtblau Nov 3 '16 at 16:52