The English prefix un- comes directly from Old English (and shares a common Indo-European root with Latin in- and Greek a-) Prefixed to an adjective A, the resulting new word means ‘not A’ and can convey either positive or negative sentiment, depending on the meaning of the adjective.
- selfish/unselfish, pretentious/unpretentious (un- has positive sentiment)
- happy/unhappy, flattering/unflattering (un- has negative sentiment)
- usual/unusual, aware/unaware (un- context-dependent sentiment)
Prefixed to a verb, un- conveys the reversal of a process:
However, not all verbs form their opposite by adding un- as a prefix. For example
You can’t unbreak a teapot, you can only repair it. (Perhaps the special context of watching a film in reverse would lend itself to such a usage ‘watch the teapot unbreak in frame 254.’ ??) Notice that there is symmetry for the associated adjectives — an object is either in a state of being broken or intact, or has the potential to be in one of these states.
Other examples of verbs that are not symmetrical with respect to un- include
You must dirty, retard, save, or retain. Similarly, verbs that denote speech acts are not symmetrical with respect to un-.
You can only renege, retract, apologize or divorce. Verbs that describe mental processes also don’t have corresponding opposites formed with un-.
The natural opposite of remember is forget, and there is the related misremember which implies recall of something not factual. (More on mis- in a moment.) Dream is more difficult; perhaps the opposite of dreaming is realizing? There seems to be no natural concept corresponding to a reversal or opposite of the event of seeing. In summary, it appears that English uses un- only with verbs that describe events which are simple, reversible physical processes, seemingly ignoring the arrow of time (even though each act of covering/uncovering, folding/unfolding, winding/unwinding is indeed moving in one direction through time).
But what about the prefix dis-? Its occurrence with verbs doesn’t appear to conform to the above patterns. The following symmetrical pairs include both speech act verbs and mental process verbs.
Allow, please, regard and invite entered English from Old French, along with the Latin-derived prefix dis- which meant ‘not’. Dislike, however, is a hybrid form that replaced the native English mislike, which was at one time the opposite of like. The native English prefix mis- meant ‘wrongly, in error’ and we see it today in the verbs misjudge, misremember and probably mistake.
- I took him for an honest man
- I mistook him for an honest man