closed system

13 LETTERS · STARTS WITH C

closed system is a valid 13-letter word worth 20 points in Scrabble and 22 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

C3L1O1S1E1D2S1Y4S1T1E1M3

3 + 1 + 1 + 1 + 1 + 2 + 0 + 1 + 4 + 1 + 1 + 1 + 3 =20 PTS

DOUBLE WORD → 40TRIPLE WORD → 60

MEANING

What does closed system mean?