TETRAD is a playable word

tetrad Scrabble® Dictionary

noun
pl. tetrads
a group of four
(adjective) tetradic
58 Playable Words can be made from "TETRAD"
   2-Letter Words (12 found)
   3-Letter Words (19 found)
   4-Letter Words (14 found)
   5-Letter Words (10 found)
   6-Letter Words (3 found)