vortex and vorticity

Vorticity is a vector that defines what is happening in spinning fluids.
This article from Princeton says it all:
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Vortex is the actual phenomenon of spinning fluids that can be as large as a galaxy or or as simple as water going out of the sink.
Here is a fine video of toroidal vortices. There are more links to useful info on the site. Click 'show more' below the video.