|This article does not cite any references or sources. (March
2010)| A jet is an efflux of fluid that is projected into a
surrounding medium, usually from some kind of a nozzle, aperture
or orifice. Jets can travel long distances without dissipating.
In the Earth's atmosphere there exist jet streams that travel
thousands of miles. Jet fluid has higher momentum compared to
the surrounding fluid medium. In the case where the surrounding
medium is assumed to be made up of the same fluid as the jet,
and this fluid has a viscosity, then the surrounding fluid near
the jet is assumed to be carried along with the jet by a process
called Entrainment (hydrodynamics). See also  - Jet stream, a
high level wind in the Earth's atmosphere - Jet engine, any
machine propelled by a jet - Jet nozzle, how a jet is formed -
Jet damping, a jet carries away angular momentum from a device
emitting it - Jet of blood - Pijush K. Kundu and Ira M. Cohen,
"Fluid mechanics, Volume 10", Elsevier, Burlington, MA,USA
(2008), ISBN 978-0-12-37