Prefixes

1. With the meaning 'not'
Prefixes (un-, in-, il-, ir- and dis-) are often used to give adjectives (and some verbs and nouns) a negative meaning. Here are common examples:
+ un- is used with many different word:
   happy          unhappy
   friendly        unfriendly
   able             unable
   employed     unemployed (without a job)
   tidy              untidy (= not in order, in a mess)
+ im- is used before some words beginning with m or p:
   polite         impolite (rude)
   patient       impatient
   possible     impossible
+ il- is used before some words beginning with l
   legible       illegible (= cannot be read because the writing is very bad)
   legal          illegal (= it's against the law)
+ ir-is only used before some words beginning with r
   responsible      irresponsible
   regular             irregular
+ dis- is used before some adjectives
   honest       dishonest
   like           dislike
   agree        disagree
+in- is used before a limited number of words
   visible        invisible (= cannot be seen)
   correct      incorrect

2. Other verb prefixes with specific meanings
+ re- (= again)
   My homework was terrible, so I had to redo it.
   The shop closed down but with reopen next month.
   I failed my exam but I can retake (or redo/resit) it next year.
+ over- (= too much)
   I think my boss is overdoing it at the moment (=working too hard)
   I went to bed very late and I overslept (=slept too long) this morning.
   The shop assistant overcharged me (=asked me for too much money)
+ mis- (= badly or incorrectly)
   I'm afraid I misunderstood what he said.
   Two of the students misread the first question.

Some examples:
_ I'm sorry, I missunderstood her message completely.
_ We unpack as soon as we got to the hotel, then went out for a walk.
_ She was here a minute ago, but then she disappeared. I'm afraid I don't know where she is now.
_ We normally have opinions but I disagree with him totally on the subject of drugs.
_ My homework was so bad that I'll have to redo it.
_ Apparently (hinh nhu) her alarm clock didn't ring and she overslept.
_ She finally managed to unlock the door and we were able to go inside.
_ I dislike the film, but the others enjoyed it.
_ I don't think I'll pass the exam, but I can always redo/retake it in September.
_ The post office shuts for lunch (-v- close) but it should reopen at 2.00 p.m.
_ She's overworking at the moment. She really needs a holiday and a complete break from her job.
_ My sister wrapped up (v- goi, boc, bao boc) my present so well that it took me about five minutes to unwrap it.

3. Many other prefixes are used in English. Here is a list of prefixes which are useful in helping you to understand unfamiliar words.