ultra beyond, extreme, more than ultrahigh – extremely high; ultramodern – more modern than anything else; ultrasonic – sound waves beyond human hearing.

un not,opposite of, lacking unabridged – not shortened; unfair – opposite of fair; unfriendly – lacking friendliness.

uni one, single unicycle – a vehicle with one wheel; unilateral – decided by only one person or nation; unique – the only one of its kind; unison – as one voice.

urb city suburb – residential area on the edge of a city; urban – relating to a city; urbanology – the study of city life.