In fluid dynamics, a siphon is a tube or pipe used to transport liquid from a container or source at a higher elevation to a lower elevation, provided the liquid level at the source is above the terminal point. The operation relies on the principles of atmospheric pressure and gravity. When the tube is filled with liquid and correctly positioned, the atmospheric pressure acting on the surface of the liquid at the higher end pushes the liquid up the tube and over the crest, where gravity takes over, causing the liquid to flow down to the lower point. This mechanism allows fluid transfer through a continuous U-shaped conduit without requiring external mechanical pumping, provided the liquid remains continuous and atmospheric pressure is maintained on the source liquid.