n.
Pronunciation: ˌ te-tr ə - ' h ē -dr ə n
Function: noun
Inflected Form: plural -drons or -dra \ -dr ə \
Etymology: New Latin, from Late Greek tetraedron, neuter of tetraedros having four faces, from Greek tetra- + hedra seat, face ― more at SIT
Date: 1570
: a polyhedron that has four faces
tetrahedron