Is there any general rule how to choose between negation prefixes?
Sometimes it's un- like in unpopular or unhealthy, while in other cases it's in- (and its variants) like in impossible or irrelevant.
Is there any general rule how to choose between negation prefixes?
Sometimes it's un- like in unpopular or unhealthy, while in other cases it's in- (and its variants) like in impossible or irrelevant.
This was a thought provoking question, but after some thinking I have to say I do not believe there is any rule that covers the majority of cases. It just needs to be learned through practice.
If the adjective is Latin or French you may assume that the prefix is in- or one of its variants (n easily changes, influence of the following consonant). Possibilis/e is a Latin adjective, so you have possible and impossible.
"healthy" is neither Latin nor French so you have "unhealthy".
Added: This is only a rule of thumb. There are cases where you have un- + a Latin adjective. See comment below. So when in doubt you have to consult the dictionary.
http://inmadom-myenglishclass.blogspot.de/2011/03/negative-prefixes-before-adjectives.html
My assumption is when the negative adjective was alredy a current word in Latin or is in the Latin dictionary then we have the prefix in- and its variants im/il/ir-. If the word was formed later, maybe around 1600 as unpopular then the English prefix un- is used. But I admit I am not sure whether this assumption holds water.