Least

Part of speech: adjective (a.)

Smallest, either in size or degree; shortest; lowest; most unimportant; as, the least insect; the least mercy; the least space.

Part of speech: adverb (adv.)

In the smallest or lowest degree; in a degree below all others; as, to reward those who least deserve it.

Part of speech: conjunction (conj.)

See Lest, conj. [Obs.] Spenser.