Is box spring one word?

In the term "box-spring sets," you have a hyphenated adjective mondifying a noun, sets. In the term "box spring base," you have a three-word noun, if I may call it that.

What does bedspring mean?

Definitions of bedspring. (usually plural) one of the springs holding up the mattress of a bed. types: box spring. a coiled bedspring in a frame that is covered with cloth.