additive primary

16 LETTERS · STARTS WITH A

additive primary is a valid 16-letter word worth 27 points in Scrabble and 29 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

A1D2D2I1T1I1V4E1P3R1I1M3A1R1Y4

1 + 2 + 2 + 1 + 1 + 1 + 4 + 1 + 0 + 3 + 1 + 1 + 3 + 1 + 1 + 4 =27 PTS

DOUBLE WORD → 54TRIPLE WORD → 81

MEANING

What does additive primary mean?