hinge upon

VERB /hɪndʒ_ə'pɑn/
10 LETTERS · STARTS WITH H

hinge upon is a valid 10-letter word worth 15 points in Scrabble and 19 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
H4I1N1G2E1U1P3O1N1
4 + 1 + 1 + 2 + 1 + 0 + 1 + 3 + 1 + 1 =15 PTS
DOUBLE WORD → 30TRIPLE WORD → 45
MEANING

What does hinge upon mean?