Groups comparison

Friendly Fire - 1979 to 2018
Player can attack their own side purposefully or by accident or be attacked themself in similar manner.

Purposeful friendly fire(Beneficial friendly fire;Useful friendly fire) - 1997 to 2015
Friendly fire can under certain circumstances have beneficial or otherwise useful effects.

Friendly fire: Full - 2005 to 2016
Friendly fire delivers full damage potential of the attacks to friendlies as well.

Friendly fire: Optional - 2005 to 2016
Friendly fire can be enabled and disabled at will. Usually a server/host setting in multiplayer games and not configurable per player.

Friendly fire: Reduced - 2005 to 2016
Friendly fire delivers only a portion of the full power of the attacks to friendlies, effectively still making friendly fire unwanted but less devastating.

Friendly fire: Penalty - 2010 to 2016
Player is penalized for any friendly fire they do.