Negative Words

In English, the prefixes in and un, along with others, are used to negate certain root words. The antonym of sane, for example, is insane, while the antonym of stoppable is unstoppable. However, some words that appear to be negated with prefixes have no positive. The opposite of inchoate, for example, is not choate - there is no such word.

debunk	defenestrate	dejected	disconsolate	dishevelled	dismantle
dismayed	disparate	feckless	gormless	impetuous	impromptu
inane	incessant	inchoate	incognito	incommunicado	indomitable
ineffable	inert	infernal	inhibited	innocent	innocuous
insidious	insipid	insouciant	intact	invert	misgivings
misnomer	nonchalant	noncommittal	nondescript	nonpareil	nonplussed
unbeknownst	unnerved	unscathed	unswerving	untold
Words With Uncommon Positive Forms The following words do have positives, formed by removing the negating prefix, but the positive forms of these words are very rare or have fallen into disuse
disarray	disconcerting	immaculate	impeccable	inadvertent	incapacitated
incorrigible	inept	inevitable	inscrutable	insensate	insufferable
interminable	reckless	unbridled	uncouth	unflappable	unfurl
ungainly	unkempt	unmitigated	unrequited	unruly	unthinkable
untoward	unwieldy
Special Cases An interesting special case is indefatigable, whose antonym is not defatigable but rather fatigable. The word inflammable is another interesting special case. Stripping off the prefix does not create an antonym but rather a synonym: flammable. This idiosyncrasy of English seems insidious (!) until one realises that the prefix in means something else in this case; the word inflammable means 'able to be inflamed.'