vortex
The flow has circulation Γ but is, perhaps surprisingly, irrotational, which highlights that curl measures local rather than global rotation. For a diagram see singularity (fluid dynamics).
- unitary matrix
- unitary ratio
- unit circle
- unit cube
- unit matrix
- unit square
- unit vector
- unity
- univalent
- universal covering space
- universal gravitational constant
- universal machine
- universal quantifier
- universal set
- unknot
- unknown
- unstable equilibrium
- upper bound
- upper limit
- upper triangular matrix
- Urysohn's lemma
- utility
- utility function
- V
- V4