The primary meaning of stream is a body of water, confined within a bed and banks and having a detectable current. Stream is the umbrella term used in the scientific community for all flowing natural waters.

By extension, a stream is any steady flow or succession of material. It could be water, air, radio signal, words (as in "a stream of abuse") etc.. The word has also some specialized senses:

• streaming media is a way of delivering radio and television over the Internet.
• High speed streams of air in the upper atmosphere are called jet streams.
• Ocean currents are sometimes referred to as streams, e.g. the Gulf Stream.
• standard streams is a computing term.