- (computing) Represents what would normally be a space ] [ in computing.
- My email address is firstname.lastname@example.org.
- (Internet slang) Sometimes used to indicate the start and end of portions of plain text that would be underlined if formatting was available.
- That's _really_ amazing!
- (programming) Especially as a prefix, denotes a special identifier such as a global or private variable or a reserved symbol.
- Usually called "underscore"