A prefix is placed at the beginning of a word to modify or change its meaning.
Here are 7 common prefixes in English, together with their basic meaning and
some examples.
- counter- meaning: opposition, opposite direction example: counter-attack, counteract
- extra- meaning: outside, beyond example: extracurricular, extramarital
- hemi- meaning: half example: hemisphere
- inter- meaning: between, among example: interact, interchange
- non- meaning: absence, negation example: non-smoker, non-alcoholic
- post- meaning: after in time or order example: postpone
- re- meaning: again example: repaint, reappraise, reawake
http://www.englishclub.com/vocabulary/prefixes.htm