- Universalist
- Unfaithful
- Unfalsifiable
- Unfavourably
- Unflagging
- Unflappable
- Unflattering
- Unflinching
- Unformed
- Unforthcoming
- Unfortunately
- Unfounded
- Unfriendliness
- Unfurnished
- Ungraciously
- Ungrammatical
- Unhappy
- Unheeded
- Unhestitating
- Unhindered
- Unhoped-for
- Unibrow
- Unidiomatic
- Uniform
- Unilateral
- Uninhabited
- Unintelligent
- Unintentional
- Uninviting
- Unionist
- Unionistic
- Unisex
- Unison
- United arab emirates
- Uniting
- Univalent
- Universal access
- Universal serial bus
- University
- Unkempt
- Unkind
- Unkindly
- Unlace
- Unlawfully
- Unleash
- Unleavened rice cake
- Unlettered
- Unliquidated
- Unlit
- Unlucky
- Unmake
- Unman
- Unmarried person
- Unmarried youth
- Unmeaning
- Unmerited
- Unmistakably
- Unmolested
- Unnameable
- Unnecessary
- Unnecessary expenditure
- Unnerve
- Unnervingly
- Unofficial
- Unopposed
- Unorganised
- Unorious
- Unorthodoxy
- Unpaid
- Unparalleled
- Unpeeled
- Unperturbed
- Unpick
- Unpleasant
- Unplesant
- Unpolluted
- Unprecedented
- Unprecedentedly
- Unpredictable
- Unprejudiced
- Unpremeditated
- Unprepared
- Unpreparedness
- Unproductive
- Unproductively
- Unprofessionally
- Unprofitable
- Unread
- Unreasoning
- Unrehearsed
- Unrelated
- Unrequited
- Unrestricted
- Unripened
- Unrivaled
- Unruffled by waves
- Unruliness
- Unruly
- Unsaleable
- Unsalted