subtraction logarithm

21 LETTERS · STARTS WITH S

subtraction logarithm is a valid 21-letter word worth 30 points in Scrabble and 36 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
S1U1B3T1R1A1C3T1I1O1N1L1O1G2A1R1I1T1H4M3
1 + 1 + 3 + 1 + 1 + 1 + 3 + 1 + 1 + 1 + 1 + 0 + 1 + 1 + 2 + 1 + 1 + 1 + 1 + 4 + 3 =30 PTS
DOUBLE WORD → 60TRIPLE WORD → 90
MEANING

What does subtraction logarithm mean?

1