fruit body

This term is a technical biological descriptor used primarily in mycology to distinguish the visible, reproductive part of a fungus from the vegetative mycelium. While a layperson might use the word "mushroom" to describe the entire organism, a scientist uses "fruit body" to specify the structure responsible for spore dispersal.

Because it is a compound noun consisting of a modifier and a head noun, the pluralization occurs on the word "body." It is used in formal scientific contexts, textbooks, and field guides to describe the morphology of basidiomycetes and ascomycetes.