Two linesmen are used to call offside, offside passes, icing, and handle all face-offs not occurring at center ice. Although they don't call penalties, they can recommend to the referee that a penalty be called.
official (in tennis or soccer or football) who assists the referee is some way (especially by watching for off-sides or out of bounds)
Two officials who assist the referee. The linesmen patrol the touchlines and signal when the ball is out of bounds, a player is offside or a foul has been committed.
One of two on-ice officials responsible for calling offsides, icing, dropping the puck during faceoffs and breaking up fights.
One of the two officials primarily responsible for calling icing and offside violations. The linesmen also conduct most faceoffs, separate fighting players, and may inform the referee of fouls, but they cannot themselves call penalties.
Secondary official who makes determinations on icing and offsides calls and is empowered to call a minor penalty if a team has too many men on the ice.
Officials that travel the sidelines with a small flag in their hand to signal the referee when the ball goes out of bounds, or when they see an offside or any other violation of a rule. The final call is always up to the referee.
the referee's assistants. These officials wear black and white striped shirts, with no armbands. Their duties are the calling of offside, and icing calls, and where necessary assisting the referee to carry out his duties.