under (adv) — sense 4 In or to a lower or subordinate position, or a position beneath or below something, physically or figuratively.
under (noun) — sense 10 The amount by which an actual total is less than the expected or required amount.
under (noun) — sense 12 A bet that a particular sporting statistic, such as points scored in a game, will be below a certain stated value.
under (prep) — sense 2 Beneath; below; at or to the bottom of, or the area covered or surmounted by.: Below the surface of.
understanding (noun) — sense 1 The act of one that understands or comprehends; the mental process of discernment of meaning.
understanding (noun) — sense 2 Reason or intelligence; ability to grasp the full meaning of knowledge; ability to infer.
understand (verb) — sense 1 To know the meaning of; to parse or have parsed correctly; to comprehend.
understand (verb) — sense 2 To know the meaning of; to parse or have parsed correctly; to comprehend.: To know the meaning of.
unfortunately (adv) — sense 2 Used (as a parenthetical word, often a sentence adverb) to express disappointment, compassion, sorrow, regret, or grief.
union (noun) — sense 3 Something united, or made one; something formed by a combination or coalition of parts or members; a confederation; a consolidated body; a league.
unique (noun) — sense 4 A thing without a like; something unequalled or unparallelled; one of a kind.