Num Lock or Number Lock (⇭) is a key on the numeric keypad of most computer keyboards. It is a lock key, like Caps Lock and Scroll Lock. Its state affects the function of the numeric keypad commonly located to the right of the main keyboard and is commonly displayed by an LED built into the keyboard.

Short for numeric lock or number lock, the Num key, Num Lock, or Num Lk key is on the top-left corner of a keyboard's numeric keypad. The Num Lock key enables and disables the numeric pad. When Num Lock is enabled, you can use the numbers on the keypad. When Num Lock is disabled, pressing those keys activates those keys' alternate functions.

Num Lock is a toggle key, which means it gets activated or deactivated when you press it. Num Lock’s primary function is to switch the keyboard input between Numerical values and some other functionalities like scrolling on the Numeric Keypad. When Num Lock is enabled, pressing the numeric pad key results in numbers as input.