- Turing machine
- Turing reduction
- Tutte graph
- Tutte polynomial
- twist mapping
- twist of elliptic curve
- twist theorem
- twisting sheaf
- two dimensional system
- two way classification
- two-person constant-sum game
- two-person game
- two-person general sum game
- two-person zero-sum game
- two-point distribution
- two-sided generator
- two-sided search
- two-sided surface, bilateral surface
- two-sided test
- two-stage estimate
- two-way channel
- two-way communication
- two-way layout
- type
- type [of entire function
- type of an universal algebra
- type-function
- U-estimator
- u-invariant of a field
- u-test
- UFD, unique factorization domain
- ultrabornologic space
- ultradistribution
- ultrafilter
- ultrahyperbolic equation
- ultraparabolic equation
- ultrapower
- ultraproduct
- umbilical point
- unary operation
- unbalanced assignment problem
- unbalanced transportation problem
- unbiased confidence interval
- unbiased confidence region
- unbiased estimate
- unbiased test
- unbounded linear operator
- unbounded lag
- unbounded reward model
- unbounded solution