Britannia

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