U
- U-dualityIn physics, U-duality (short for unified duality) is a symmetry of string theory or M-theo
- Ultra low expansion glassUltra low expansion glass (ULE) is a registered trademark of Corning Incorporated. ULE has
- UltramarineDeep blue pigment
- Ultrasonic nozzleType of spray nozzle
- UltrasoundSound waves with frequencies above the human hearing range
- UltravioletForm of electromagnetic radiation
- Ultraviolet catastropheClassical physics prediction that black body radiation grows unbounded with frequency
- UncertaintySituations involving imperfect or unknown information
- Uncertainty principleFoundational principle in quantum physics
- Underwater acousticsStudy of the propagation of sound in water
- Unequal hoursA system where hour lengths are unequal or not all 60 minutes
- Unified field theoryField theory in physics that aims to unify the fundamental forces and particles
- Unit cellRepeating unit formed by the vectors spanning the points of a lattice
- Unit of lengthReference value of length
- Unit vectorVector of length one
- Unitarity (physics)In quantum physics, unitarity is (or a unitary process has) the condition that the time ev
- Unitary matrixComplex matrix whose conjugate transpose equals its inverse
- Unitary operatorSurjective bounded operator on a Hilbert space preserving the inner product
- Unitary transformation (quantum mechanics)Important mathematical operations in quantum mechanics
- United States Glass CompanyAmerican glassmaking conglomerate
- Universal wave functionQuantum state of the entire universe
- Unparticle physicsSpeculative theory of non-particle matter
- Unpolarized lightUnpolarized light is light with a random, time-varying polarization. Natural light, like m
- Until the End of Time (book)Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe is
- Up quarkType of quark
- Upsilon mesonThe Upsilon meson (ϒ) is a quarkonium state (i.e. flavourless meson) formed from a bottom