newton's third law

NOUN
18 LETTERS · STARTS WITH N

newton's third law is a valid 18-letter word worth 25 points in Scrabble and 27 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
N1E1W4T1O1N1'0S1T1H4I1R1D2L1A1W4
1 + 1 + 4 + 1 + 1 + 1 + 0 + 1 + 0 + 1 + 4 + 1 + 1 + 2 + 0 + 1 + 1 + 4 =25 PTS
DOUBLE WORD → 50TRIPLE WORD → 75
MEANING

What does newton's third law mean?