— barren
— impotent
— sterilised
— sterilized
— unafraid
— unbearable
— unbridled
— unfair
— unfairly
— unfertilised
— unfertilized
— unforced
— unforeseen
— unformed
— unfortunate
— unfruitful
— unfurl
— uniformity
— uniformly
— unimpregnated
— universal
— universe
— unperturbed
— unproductive
— unvaried
— unvarnished
— unvarying
— unversed
— unwavering