better half

NOUN /bɛtər_hæf/
11 LETTERS · 2 SYLLABLES · STARTS WITH B

better half is a valid 11-letter word worth 18 points in Scrabble and 19 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
B3E1T1T1E1R1H4A1L1F4
3 + 1 + 1 + 1 + 1 + 1 + 0 + 4 + 1 + 1 + 4 =18 PTS
DOUBLE WORD → 36TRIPLE WORD → 54
MEANING

What does better half mean?