Refers to one side of a pair, a road, a street, a vehicle, or a bilateral object. Often used in contrast with 両側 (both sides).
道路の片側だけ工事中だ。
Only one side of the road is under construction.
One side of the earphones broke.
Bicycles are lined up on one side of the road.
The hair is long on only one side.
The car pulled over to one side and stopped.