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.

1. counter-
meaning: opposition, opposite direction
example: counter-attack, counteract

2. extra-
meaning: outside, beyond
example: extracurricular, extramarital

3. hemi-
meaning: half
example: hemisphere

4. inter-
meaning: between, among
example: interact, interchange

5. non-
meaning: absence, negation
example: non-smoker, non-alcoholic

6. post-
meaning: after in time or order
example: postpone

7. re-
meaning: again
example: repaint, reappraise, reawake

See more prefixes and their meanings at:
http://www.englishclub.com/vocabulary/prefixes.htm
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