'

In C-based programming languages, this denotes a single character, like 'c', where c is any character.
In Perl, this denotes a string that should not translate any escaped codes.
In QuakeC, this indicates a vector, like 'x y z', where x, y, and z are the vector's components.

In several human languages, this is used for contractions, omitted letters, possession, and other things.

see also:   "   ‘   ’