A prefix of Old English origin meaning "against", "back", "in return", "away", represented in Modern English by a-, an-, on-, and in altered form by the reverse-action prefix un- (e.g. unbuckle). Also as the initial letter d in dread (< Old English ondrǣdan).
do the opposite of, reverse (a specified action)
contrary to or contrasted against traditional norms; unconventional; alternative
Used to form temporary names of elements (such as unbiunium) whose existence has been predicted, and have not yet been given a trivial name.
absent; lacking; not; negative
deprive of, release from, free from, remove from, extract from
intensifying a verb that already suggests opposition or removal
not
Used to form large numbers as the first in the sequence.