by Sentenceworks
Hyphen
With Compound Modifiers
Sometimes words can play two roles; for instance, American can be a noun or an adjective. When there are several of these words together, hyphens can make it clear as to which word is playing which role.
Correct: The table was covered by twenty odd books.
In this sentence, the books are being described as odd.
Correct: The table was covered by twenty-odd books.
In this sentence, there are approximately twenty books covering the table.
Incorrect: It is recommended you not take down any load bearing walls when renovating.
In this sentence, it sounds like you shouldn’t take down any load which is holding up a wall. A hyphen should be inserted between load and bearing, so we understand not to take down any walls which are holding up a load.
Correct: The room was like a heavily decorated chocolate box.
Because the adverb heavily is clearly modifying the verb decorated, no hyphen is required in this sentence.
With Noun, Adjective or Adverb + Present Participle
When using a noun, adjective or adverb and a present participle (a word ending in -ing), we often have to put a hyphen between the two words to make it clear as to which word is modifying which.
Incorrect: There are some beautiful looking flowers in the garden.
A hyphen should be inserted between beautiful and looking.
Incorrect: Fast acting medication can be useful when one has a headache.
A hyphen is required between the adverb fast and the present participle acting.
With Compound Expressions
A compound expression is two words which are put together to make a new adjective, and is in common use. These two words should be hyphenated to clarify the intent of the new meaning. Some examples of compound expressions are time-sensitive, long-lasting, and life-long.
Incorrect: The small child was sitting on the sofa with his ever present blanket.
In this sentence, ever and present are put together to form the compound expression ever-present; a hyphen should be inserted between ever and present.
Incorrect: One must be self motivated in order to be a good student.
Self and motivated are being used as a compound expression in this sentence; a hyphen should be inserted between the two words: self-motivated.
Correct: It’s a really bad idea to drive the wrong way on a one-way street.
One-way should be hyphenated as it is a compound expression.
Compound Expression with Noun + Past Participle
When a noun is put together with a past participle (a verb ending in –ed), this results in a compound adjective. Compound adjectives should always be hyphenated, so the reader can distinguish them from the original words. For instance, when we connect the noun community with the verb based, it makes the compound adjective community-based.
Incorrect: Wind powered generators can be excellent sources of electricity.
The noun wind and the past participle powered are being used as a compound adjective to modify generators. There should be a hyphen between wind and powered: wind-powered.
Correct: Many veterinarians find meat-fed cats to be quite healthy.
In this sentence, meat-fed is the compound adjective used to modify cats, so the hyphen is correctly used.
Compound Adjective with Numbers
When numbers are used as the first part of a compound adjective, they should have a hyphen connecting them to the noun which follows them. This applies whether the number is written in words or in digits.
Incorrect: The president of the company gave a 10 minute speech to the Board of Directors.
As the number 10 is used as part of the compound adjective modifying speech, there should be a hyphen between 10 and minute: The president of the company gave a 10-minute speech to the Board of Directors.
Incorrect: He is knowledgeable in thirteenth century politics.
There should be a hyphen between thirteenth and century.
Incorrect: The boy threw a rock at the second story window.
Both second and story are being used as adjectives to modify window, so a hyphen is required: second-story window.
Correct: I live on the second story of the house.
A hyphen is not required here because second is the only modifier of story; it is not part of a compound adjective.
N.B. A hyphen is not required if the number is the second word in the compound adjective.
Incorrect: He is a victim of Type-2 diabetes.
A hyphen is not required in this compound modifier because the number is the second element in the compound adjective.
Compound Adjective with High or Low
When using high or low as part of a compound adjective, a hyphen should be inserted between high – or low – and the word which it modifying. Some examples of compound adjectives using high and low are: high-level/low-level and high-impact/low-impact.
Incorrect: Low flying airplanes contribute to the noise pollution in the area.
Low is modifying flying, so there should be a hyphen between the two words: low-flying. The compound adjective is modifying airplanes.
Correct: This car runs best on high-octane gasoline.
As it is a compound adjective, high-octane is correctly hyphenated.
Compound Adjective with Comparatives or Superlatives
Some comparatives and superlatives are accomplished by using a suffix (e.g. highest, smaller); if these words are used in a compound adjective, they should hyphenated. Some comparatives and superlatives use more or most; these do not generally require a hyphen, although some older common phrases may use one.
Incorrect: It is generally preferable to have a position as a higher level executive than as a menial worker.
The compound adjective which uses a comparative, higher-level, should be hyphenated so it clearly modifies executive.
Correct: There are more important reasons for taking care of your health than longevity.
In this sentence, more important is clearly defining reasons, so a hyphen is not necessary.
Correct: Best-laid plans often fall apart.
Correct: Best laid plans often fall apart.
As it is an older common phrase, best-laid may or may not use a hyphen.
Compound Adjective with Fractions
When using a fraction (i.e. half or quarter) as part of a compound adjective, it should be hyphenated.
Incorrect: I half wanted to commit a felony.
Half and wanted are both parts of a compound adjective which is modifying to commit. There should be a hyphen between half and wanted: half-wanted.
Correct: A quarter-million dollars is still a large amount of money.
Because it is a compound adjective which is modifying dollars, quarter-million requires a hyphen.