open sentence

13 LETTERS · STARTS WITH O

open sentence is a valid 13-letter word worth 16 points in Scrabble and 21 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

O1P3E1N1S1E1N1T1E1N1C3E1

1 + 3 + 1 + 1 + 0 + 1 + 1 + 1 + 1 + 1 + 1 + 3 + 1 =16 PTS

DOUBLE WORD → 32TRIPLE WORD → 48

MEANING

What does open sentence mean?