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Hyphens in Prefixes
Should I put a hyphen after a prefix?
A prefix is a half word (e.g., anti-, ex-, post-, pre-) placed before a word to modify its meaning. Most prefixed words can be written with or without a hyphen after the prefix.General Guideline with Prefixes
As a general guideline, avoid the hyphen if you can, but if the unhyphenated version is a spelling mistake (let your spellchecker do its job) or looks too unwieldy for you, use a hyphen.Here are some fixed rules:
- Always use a hyphen with "ex-" and "self-,"
- Never allow ambiguity (e.g., write "re-press the shirt" not "repress the shirt")

More Guidance with Hyphens in Prefixes
There is often confusion over whether a hyphen should be used with a prefix. In other words, should you write "re-consider" or "reconsider," or "anti-aircraft" or "antiaircraft"?Unfortunately, there is no simple rule governing this, but here are some guiding principles.
Guiding Principles for Hyphens with Prefixes
If it's not a spelling mistake to avoid the hyphen and you can bear how the word looks without it, then avoid the hyphen.Often, it's your choice whether to use a hyphen. Lots of prefixed words can be written with or without a hyphen. Here is the guiding principle:
Applying the Principle
Here are some examples to explain the guiding principle:- antiaircraft ("Antiaircraft" is not wrong, but it looks a little unwieldy. If you feel the same way, write "anti-aircraft.")
- proactive
- prehistoric
- ultraviolet
Detailed Guidance on Hyphens with Prefixes
Use a Hyphen with a Proper Noun
If your prefix sits before a proper noun, use a hyphen. For example:- un-British
- pro-Nazi
Do Not Allow the Same Vowel to Double Up
If the prefix ends in the same vowel that the root words starts with, separate them with a hyphen. For example:- semi-industrious
- re-enter
- ultra-argumentative
- coordinate
- cooperate
- coowner
You Can Let Different Vowels Double Up
When a prefix ends in a vowel and the root word starts with a different vowel, omit the hyphen. For example:- proactive
- reactivate
- semiautonomous (However, if your spellchecker doesn't like it or you cannot bear how it looks, go for a hyphen. For many, " semiautonomous" looks too unwieldy.)
Use a Hyphen with "Ex" and "Self"
The prefixes "ex" and "self" are followed by a hyphen. For example:- ex-husband
- self-aware
Eliminate Ambiguity Every Time
If the unhyphenated version could be confused with a different word, add the hyphen. (This is most common with the prefix "re." For example:- re-cover
/ recover
(If there were no hyphen in "re-cover," it could be confused with "recover," meaning "return to a normal state.")
- re-press
/ repress
(If there were no hyphen in "re-press,"Could be confused with "repress," meaning "subdue with force.")
Enjoy the Leniency
Most prefixed words exist in both forms. As you might have noticed in the guidelines above, it is often down to how the writer feels about the word.- The attack would take place at night as the anti-government troops did not possess infrared goggles.
Some Common Prefixes
Here are some common prefixes:Prefix | Meaning | Example |
---|---|---|
a-, an- | without | amoral, atypical |
ante- | before | antecedent, antenatal |
anti- | against | anti-establishment |
auto- | self | autopilot |
circum- | around | circumvent |
co- | with | co-conspirator, co-pilot |
com-, con- | with | companion, contact |
contra- | against | contradiction |
de- | off | delist, devalue |
dis- | not | disappear |
en- | put into | enclose, envelop |
ex- | out of, former | extract, ex-governor |
extra- | beyond, more than | extracurricular |
hetero- | different | heterosexual |
homo- | same | homonym, homophone |
hyper- | over, more | hyperactive |
il-, im-, in-, ir- | not, without | illegal, impractical, inconsiderate, irresponsible |
in- | into | insert |
inter- | between | internet, intersection, |
intra- | between | intranet, intravenous |
macro- | large | macronutrients |
micro- | small | microscope |
mono- | one | monocle |
non- | not, without | nonentity, nonstarter, |
omni- | all, every | omnipresent, omniscient |
post- | after | post-mortem |
pre-, pro- | before, forward | precede, project |
sub- | under | submarine, substandard |
syn- | same time | synchronize |
super- | above | supervisor, superhuman |
trans- | across | transmit |
tri- | three | tripod, triceratops |
un- | not | undone, unfinished, |
uni- | one | unicorn, unilaterally |
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