Some common words in the English language that begin with the letter "u" include umbrella, utopia, urine, urinary, unfazed, unlock, unzip, upon, up and under. Other words that begin with you include underwear, us, ultra, unavoidable, undecidable, unlivable and undeniable.
More complex words beginning with the letter "u" are ubiquitous, which means to be everywhere at once, undesirable or to be not worthy of desire and ulterior, meaning beneath what is seen. More words include ultimatum, a final demand or condition, umbrage, a feeling of anger caused by being offended and unabashed, or not embarrassed by something particular.
Most "u" words are proceeded by the "un" prefix. Words such as unappreciated, unapproachable, unreachable, unassailable, unattainable, unbiased, unbridled, unprecedented, underrepresented, unravel, unprincipled, unregulated, unrelenting, unresponsive, unrestrained, unruly, untitled, unadvised, uncanny, unkempt, unorthodox, unpack, unparalleled, unpromising, uncharted and unconditional all follow this format.
More commonly used, simple vocabulary beginning with the letter "u" include ugly, underline, unhappy, upside, upper and underground. Some of these words also follow the prefix "un" format. Some unusual words beginning with the letter "u" include ululation, a type of singing used in rituals, uxoricide, or the act of killing one's own wife and ugsome, or a feeling induced by something gruesome or horrible.