hinge

v. attach with a hinge; depend on, pivot; make dependant on

n. movable joint on which a door or other part turns

A hinge is a type of bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Hinges may be made of flexible material or of moving components. In biology, many joints function as hinges. They are also known as shangles in old tudorian English (the large hinges on doors). Hinge-like structures are employed in many types of movable bridges.
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Hinge n. A jointed or flexible device that allows the turning or pivoting of a part, such as a door or lid, on a stationary frame. [more]Hinge - Community and Resources

Noun
1. a joint that holds two parts together so that one can swing relative to the other
(synonym) flexible joint
(hypernym) joint
(hyponym) butt hinge
(part-holonym) exterior door, outside door
(part-meronym) pintle
2. a circumstance upon which subsequent events depend; "his absence is the hinge of our plan"
(hypernym) circumstance
Verb
1. attach with a hinge
(hypernym) attach
(derivation) flexible joint

(v. t.)
To bend.
  

(v. t.)
To attach by, or furnish with, hinges.
  

(v. i.)
To stand, depend, hang, or turn, as on a hinge; to depend chiefly for a result or decision or for force and validity; -- usually with on or upon; as, the argument hinges on this point.
  

(n.)
The hook with its eye, or the joint, on which a door, gate, lid, etc., turns or swings; a flexible piece, as a strip of leather, which serves as a joint to turn on.
  

(n.)
That on which anything turns or depends; a governing principle; a cardinal point or rule; as, this argument was the hinge on which the question turned.
  

(n.)
One of the four cardinal points, east, west, north, or south.