understand - v. to know what is meant; to have knowledge of

unite - v. to join together

universe - n. all of space, including planets and stars

university - n. a place of education that usually includes several colleges and research organizations

unless - conj. except if it happens; on condition that ("I will not go, unless the rain stops.")

until - conj. up to a time; before

up - ad. to, in or at a higher position or value

urge - v. to advise strongly; to make a great effort to get someone to do something

urgent - ad. needing an immediate¹ decision or action

us - pro². the form of the word "we" used after a preposition ("He said he would write to us.") or used as an object of a verb ("They saw us yesterday.")

use - v. to employ for a purpose; to put into action

usual - ad. as is normal or common; as is most often done, seen or heard