套 (tào): set, suit; to cover, to encase; measure word for sets

The weather suddenly turned cold, so his mother quickly pulled a thick sweater over Xiaoming to keep him from catching a chill.

Before going to bed, she took off the pillowcase and washed it, then slipped on a newly bought light blue pillowcase.

It was raining heavily outside, so before going out he put waterproof shoe covers over his shoes so his feet wouldn't get wet.

Mom put the phone into a soft rubber protective case, saying that way it won't break easily if dropped on the ground.

Every morning Grandpa goes to the park and practices a set of tai chi, his movements slow yet powerful.