Yes, tetrad is a Scrabble word!
...and is worth 7 points in Scrabble, and 7 points in Words with Friends
tetrad
Noun
1. The cardinal number that is the sum of three and one
What Scrabble words can I make with the letters in tetrad?
6 Letter Words
5 Letter Words
4 Letter Words
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3 Letter Words
2 Letter Words