- Unique
- Unisexual
- Unisonal
- Unitary system
- United with
- Unitize
- Unitude
- Unity in diversity
- Universal flood
- Unix
- Unlearn
- Unlike
- Unlisted
- Unloading
- Unloose
- Unluckily
- Unmanly
- Unmerciful
- Unmissable
- Unmoor
- Unmoved
- Unnamed
- Unnecessarily
- Unnoticed
- Unofficially
- Unorthodox
- Unpaired
- Unpalatable
- Unparliamentary
- Unpatriotic
- Unplaced
- Unplanted
- Unplayable
- Unplowed
- Unpractical
- Unpretending
- Unprincipled
- Unpronounceable
- Unprotected
- Unpunished
- Unputdownable
- Unqualified
- Unquestionably
- Unquiet
- Unravel
- Unready
- Unreal
- Unreal substance
- Unreasonably
- Unrelenting
- Unrelieved
- Unremarkable
- Unrestrainedly
- Unrighteous
- Unripe
- Unrivalled
- Unscripted
- Unscrupulously
- Unsealed
- Unseat
- Unsettle
- Unsettled
- Unshakeable
- Unshaken
- Unsightly
- Unsigned
- Unskillfullness
- Unsmoked
- Unsolved
- Unsparing
- Unsparingly
- Unspectacular
- Unstable
- Unsteadily
- Unsteadiness
- Unstinting
- Unstoppable
- Unstruck
- Unsubstantiated
- Unsuccessful
- Unsuccessfully
- Unsuitability
- Unsurprised
- Unswayed
- Unsympathetic
- Untalented
- Untested
- Unthinkably
- Untidy
- Untie
- Until now
- Untired
- Untirring
- Untroubled
- Unused
- Unusually
- Unvanquished
- Unveil
- Unveiling
- Unwarranted