Describing and explaining prefixes????

[Latinlover]

What is the best way to describe prefixes of adjectives such as un-, in-, im-, and dis? I also would like to know how to explain to my students why you would say "impatient" instead of "dispatient," or "unemployed" instead of "imenployed" for example (ie. using one prefix over another).

[josef]

First of all, this EnglishClub.com page on prefixes may help you. The page gives the essential meaning of each prefix.

Generally speaking prefixes and other affixes vary according to the origin of the root word - for example, Greek, Latin, Germanic etc. Trying to impose rules requires students to know the origin of a word, which is increasingly unlikely for native speakers and all the more so for learners.

[DavidB]

I certainly wouldn't get the students to memorize any prefixes as it would be a waste of time in my mind.

From reading and listening they will get a feel for which is correct. Also, prefixes are commonly mistaken by native speakers, so no big worry. For example, think about how many times you have heard both impatient and inpatient, or incontrollable or uncontrollable.

Plus, don;t forget about that little word "not" which can always save the day!