Siphon

The word siphon (from Ancient Greek: σίφων “pipe, tube”, also spelled syphon) is sometimes used to refer to a wide variety of devices that involve the flow of liquids through tubes – see siphon terminology – but in the narrower sense it refers specifically to a tube in an inverted U shape which causes a liquid to flow uphill, above the surface of the reservoir, without pumps, powered by the fall of the liquid as it flows down the tube under the pull of gravity, and is discharged at a level lower than the surface of the reservoir. Note that while the siphon must touch the liquid in the (upper) reservoir (the surface of the liquid must be above the intake opening), it need not touch the liquid in the lower reservoir and indeed there need not be a lower reservoir – liquid can discharge into mid-air.