persistency

NOUN
11 LETTERS · 4 SYLLABLES · STARTS WITH P

persistency is a valid 11-letter word worth 18 points in Scrabble and 20 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
P3E1R1S1I1S1T1E1N1C3Y4
3 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 3 + 4 =18 PTS
DOUBLE WORD → 36TRIPLE WORD → 54
MEANING

What does persistency mean?