hinge
n. countablen. a metal piece that connects two things, like a door and a wall, so that one of them can swing open and shut.
n. a jointed device or flexible piece on which a door, gate, or lid turns or swings. Often used metaphorically to describe a central point on which an event or situation depends.
The door squeaks because the hinge is rusty.
The carpenter carefully aligned the hinge to ensure the heavy oak door would swing smoothly without catching on the floor.
The success of the entire diplomatic mission seemed to rest on a single hinge of policy regarding international trade tariffs.
From Middle English henge (“hinge”), from Old English henġ or henġe (“hinge”), from Proto-West Germanic hangiju or hangī; compare Old English *henġe- in henġeclif (“overhanging cliff”), Old English henġen (“hanging; that upon which a thing is hung”). Akin to Scots heenge (“hinge”), Saterland Frisian Hänge (“hinge”), Low German henge (“hook, hinge, handle”), Dutch heng (“moving leaf of a hinge”), geheng (“hinge”), Middle Dutch henghe, hanghe (“hook, hinge, handle”), Scots hingel (“any attachment by which something is hung or fastened”), Dutch hengel (“hook”), hengsel (“handle”), dialectal German Hängel (“hook, joint”), German Henkel (“handle, hook”), Danish hængsel (“hinge”), Faroese hongsl (“hinge”), Icelandic hengsli (“hinge”), Norwegian hengsel (“hinge”), Swedish hängsle (“suspender”), Old English hōn (“to hang”), hangian (“to cause to hang, hang up”). More at hang.
Commonly used in the phrase 'hinge on' when functioning as a verb to indicate total dependency.