1. prefix
A prefix goes at the beginning of a word. A suffix goes at the end of a word.
Retain, detain

2. A prefix is placed at the beginning of a word to modify or change its meaning. This is a list of the most common prefixes in English, together with their basic meaning and some examples. You should use this list as a guide only, to help you understand possible meanings.

3. Prefix : anti
Meaning : opposing, against, the opposite
Examples: anti-aircraft, anti-Japanese war

4. Prefix : com, also co-, col-, con-, cor-
Meaning : with, jointly, completely
Examples: combat, codriver, cooperate

5. Prefix : de-
Meaning :down, away, completely, removal,
Examples: descend, despair, depend, de-ice, decamp

6. Prefix :dis-
Meaning :negation, removal,
Examples: disadvantage, disapproval , discourage, disappear

7. Prefix: en-
Meaning : bring into the condition of
Examples: enlighten, enlarge, enrich, widen

8. Prefix : ex- also e-, ef-
Meaning : out, upward, completely, previous
Examples: exit, exclude, expand , ex-wife

9. Prefix: in- also il-, im-, ir-
Meaning : not, without,
Examples: infertile, inappropriate, impossible,

10. Prefix : inter-
Meaning: between, among
Examples: interact, interchange ,international

11. Prefix: non-
Meaning : absence, negation
Examples: non-smoker, non-alcoholic

12. Prefix : over-
Meaning : excessively, upper, over,
Examples: overconfident, overburdened, overjoyed

13. Prefix: pre-
Meaning : before in time, place, order or importance
Examples: pre-adolescent, prelude, prewar

14. Prefix: re-
Meaning: again
Examples: repaint, retell, reawake

15. Prefix : un-
Meaning : not , reversal or cancellation of action or state
Examples: unacceptable, unreal, unhappy, unmanned ;
unplug, unmask

16. Prefix : trans-
Meaning : across, beyond
Examples: transnational, translate