unset

Remove variable or function names

Syntax
      unset [-fv] [name]

Options
      -f    The names refer to shell Functions, 
            and the function definition is removed.
            Readonly variables and functions can not be unset. 

      -v    Each name refers to a shell Variable (default)

The return status is zero unless a name does not exist or is readonly.

unset is a bash built in command.

"A good trader has to have three things: a chronic inability to accept things at face value, to feel continuously unsettled, and to have humility" ~ Michael Steinhardt

Related:

env - Display, set, or remove environment variables
echo - Display message on screen
export - Set an environment variable
function - Define Function Macros
readonly - Mark variables/functions as readonly
set - Manipulate shell variables and functions
Equivalent Windows commands: SET - Display, set, or remove Windows environment variables