What Is a Prefix?

A prefix is a word part placed in front of a base word. A prefix usually changes the meaning of the base word. Here's an example:

The prefix un added to the word happy makes a new word with a new meaning. The prefix un means not, so it changes the meaning of the word happy to not happy. Un + Happy = Unhappy

The Two Most Common Prefixes

The most common prefixes are un and re. un re

These two prefixes are the most useful for beginning spellers to learn because they appear frequently and their meanings are easy to understand.

Un means not (unhappy = not happy) or the reverse of or opposite of (as in untie).

Re means again (redo = do again) or back (as in repay).     

Handy Tips for Adding Prefixes

• The spelling of the base word never changes. Simply add the prefix to the beginning of the base word, as in the word unhappy.

• The spelling of the prefix never changes. A prefix will be spelled the same no matter what base word it is attached to. For example, if you learn to spell the prefix poly, as in polygon, you can depend on poly to be spelled the same in the words polygraph, polyester, and polygram.

• Be aware that double letters can occur. If you add the prefix un to natural, both the prefix and the base word retain their original spelling. The result is unnatural. Take a look at these other words where double letters occur:

il + logical = illogical
im + mature = immature
il + legal = illegal
un + necessary = unnecessary

Other examples: unnoticeable, illiteracy, immaterial, immeasurable, immigrant, immobile, immoral, dissatisfy, disservice, dissimilar, dissolve, irreconcilable, irredeemable, irreducible, irregular, irrelevant, irreparable, irrestistible, irresponsible, misspoke, misspell, misstep

• Watch out for prefix look-alikes. Some words contain the same string of letters as a prefix, but upon closer examination you’ll find that they are not prefixes. The re in real is not a prefix. Other examples include uncle, pretty, press, interest, reach, irony, dish, and antique.

 

Six Rules for Using Hyphens with Prefixes

A prefix is usually added directly to the base word, but sometimes a hyphen is needed. Following are six common rules for adding a hyphen between the prefix and the base word:

1. Hyphenate when the prefix comes before a proper noun or a numeral.
   
   Examples: un-American, pre-1980
   
   
2. Hyphenate when adding the prefix ex meaning former.
   
   Example: ex-president
   (Do not use a hyphen if ex means out of or away from, as in expel.)
   
   
3. Hyphenate after the prefix self.
   
   Examples: self-respect, self-assured, self-control
   
   
4. Hyphenate to separate two a’s, two i’s, or other letter combinations that might cause misreading or mispronunciation.
   
   Examples: ultra-ambitious, anti-intellectual, co-worker
   
   
5. A hyphen may be used to separate two e’s or two o’s to improve readability or prevent mispronunciation.
   
   Examples:
   co-opt and co-owner vs. coordinate
   de-emphasize vs. reenter
   
   (Note that many words with double e’s used to be hyphenated as a general rule, as in re-elect, re-establish, and pre-existing. However, current style manuals and dictionaries now tend toward “closing” the word except in cases where readability is affected. Both versions are currently accepted and listed in most dictionaries.)
   
   
6. A hyphen is sometimes used after the prefix re to prevent misreading or confusion with another word.
   
   Examples:
   re-cover vs. recover, as in Re-cover the boat when you recover from the flu.
   re-lay vs. relay, as in Please relay the message that they will re-lay the tiles.