Are There Any Rules For Using Prefixes?


3 Answers

Will Martin Profile
Will Martin answered
Yes, there are, although some things about prefixes are quite arbitrary. Unfortunately the commonest prefixes of all, un- and in- , are interchangeable and just have to be learnt.
Otherwise, there are some helpful rules, mainly about negative prefixes:
Ir- appears only before words beginning with "r" (regular, relevant)
il- is before "l" (legal, legitimate)
I'm- is before "m" or "p" (immeasurable, impossible)
A note of caution, though; while the above prefixes can only be used with the letters shown, the letters themselves are often used with other prefixes (unreliable, unlawful, unpatriotic)
mis- always has the sense of a mistake being made (misunderstand, misfire)
this- has the sense of change or difference rather than absence/lack, e.g. "dissatisfied" means that you're not happy with the quality of something that you've got, whereas "unsatisfied" suggests a lack of something. (If you're dissatisfied with your restaurant meal you complain; if unsatisfied, you order more.)
With most other prefixes, it's not so much a question of rules as of learning their meanings: Pre- means before, post- after, and so on.
thanked the writer.
Anonymous commented
In relation to in- as a prefix for words beginning with 'l'....which you suggest should take 'il'...
I believe this should be corrected to read, "words beginning with 'le', eg legitimate, legal, will take il- as the prefix. Other words beginning with 'l' but followed by a vowel other than 'e' take 'un' as the prefix (eg.unladylike, unlifelike, unloving, unlucky).
Anonymous Profile
Anonymous answered
I don't completely agree with Paulaw. There are some other "le" words that do not take the "il" prefix (mislead, unleash).
Also, there are other words with "il" prefixes that do not have "le" (illogical, illiterate).
"dislike" is an exception for the "l+another vowel" rule after the prefix "un."

I hate frustrating for my ESL students!  I just tell them to memorize and read as much as possible...
Anonymous Profile
Anonymous answered
Well, il- is used before l in words with foreign origins like legal and literate... It's too complicated to look back into the etymology so the best is to figure out what the prefix means (as mentioned above) and to memorize the words that it works with. Lucky ESL learners!

Answer Question