exchangeability

NOUN
15 LETTERS · 6 SYLLABLES · STARTS WITH E

exchangeability is a valid 15-letter word worth 33 points in Scrabble and 36 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
E1X8C3H4A1N1G2E1A1B3I1L1I1T1Y4
1 + 8 + 3 + 4 + 1 + 1 + 2 + 1 + 1 + 3 + 1 + 1 + 1 + 1 + 4 =33 PTS
DOUBLE WORD → 66TRIPLE WORD → 99
MEANING

What does exchangeability mean?