Main Difference
The main difference between Valve and Stopcock is that the Valve is a device that regulates, directs or controls the flow of a fluid or a gas and Stopcock is a valve type.
Valve
A valve is a device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.
The simplest, and very ancient, valve is simply a freely hinged flap which drops to obstruct fluid (gas or liquid) flow in one direction, but is pushed open by flow in the opposite direction. This is called a check valve, as it prevents or “checks” the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems.
Valves have many uses, including controlling water for irrigation, industrial uses for controlling processes, residential uses such as on/off and pressure control to dish and clothes washers and taps in the home. Even aerosols have a tiny valve built in. Valves are also used in the military and transport sectors.
Stopcock
A stopcock is a form of valve used to control the flow of a liquid or gas. The term is not precise and is applied to many different types of valve. The only consistent attribute is that the valve is designed to completely stop the flow when closed fully.
Valve (noun)
A device that controls the flow of a gas or fluid through a pipe.
Valve (noun)
A device that admits fuel and air into the cylinder of an internal combustion engine, or one that allows combustion gases to exit.
Valve (noun)
One or more membranous partitions, flaps, or folds, which permit the passage of the contents of a vessel or cavity in one direction, but stop or control the flow in the opposite direction
“the ileocolic, mitral, and semilunar valves”
Valve (noun)
One of the leaves of a folding door.
Valve (noun)
A vacuum tube.
Valve (noun)
One of the pieces into which certain fruits naturally separate when they dehisce.
Valve (noun)
A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, such as in the barberry.
Valve (noun)
One of the pieces or divisions of bivalve or multivalve shells.
Valve (noun)
One of the two similar portions of the shell of a diatom.
Valve (verb)
To control (flow) by means of a valve.
Stopcock (noun)
A valve, tap or faucet which regulates the flow of liquid or gas through a pipe.
Stopcock (noun)
A main shutoff for water to a home from a municipal supply. Usually these valves exist in pairs, one outside the property boundary and one inside the property boundary.
“If you have a burst pipe turn the water off at the stopcock.”
Valve (noun)
a device for controlling the passage of fluid or air through a pipe, duct, etc., especially an automatic device allowing movement in one direction only
“a valve shuts off the flow from the boiler when the water is hot enough”
Valve (noun)
short for thermionic valve
Valve (noun)
a cylindrical mechanism in a brass instrument which, when depressed or turned, admits air into different sections of tubing and so extends the range of available notes.
Valve (noun)
a membranous fold in a hollow organ or tubular structure, such as a blood vessel or the digestive tract, which maintains the flow of the contents in one direction by closing in response to any pressure from reverse flow
“the aortic valve”
Valve (noun)
each of the halves of the hinged shell of a bivalve mollusc or brachiopod, or of the parts of the compound shell of a barnacle.
Valve (noun)
each of the halves or sections into which a dry fruit (especially a pod or capsule) dehisces.
Stopcock (noun)
an externally operated valve regulating the flow of a liquid or gas through a pipe, in particular one on the water main supplying a house
“in many houses, the main stopcock is situated under the kitchen sink”