1. A combining form or prefix to nouns to express the absence of, reversal, cancellation, deprivation, separation, lack of, or the contrary of, that which the noun signifies; as, unbelief, unfaith, unhealth, unrest, untruth, and the like.

An inseparable verbal prefix used to express the contrary, and not the simple negative, of the action of the verb to which it is prefixed; as in unbend, uncoil, undo, unfold.

Compare: in-, non-.

In- is prefixed mostly to words of Latin origin, or else to words formed by Latin suffixes; un- is of much wider application, and is attached at will to almost any adjective, or participle used adjectively, or adverb, from which it may be desired to form a corresponding negative adjective or adverb, and is also, but less freely, prefixed to nouns. Un- sometimes has merely an intensive force; as in unmerciless, unremorseless.

2. <chemistry> denoting 'one', combined with other numerical roots (nil = 0, bi = 2, etc.) to form names of recently discovered elements based on the atomic number (e.g. unnilhexium = element 106).

Origin: OE. un-, on-, akin to D. ont-, G. ent-, OHG. int-, Goth. and-.

(05 Feb 2009)

uML, umol, UMP, UMP synthase, UMTS < Prev | Next > unabsorbable, unalist, unarmed rostellum

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