A hyphen is used mainly to join two or more words to form a new, compound word. A hyphen can also be used to join a prefix to a root word as well as mark line breaks. Other uses for hyphens include indicating a range of numbers and combining sets of numbers into a single unit. No spaces should be used on either side of a hyphen with the exception of a hanging hyphen. Finally, don’t confuse hyphens with dashes (see below).
Use a hyphen to form a compound word
The most common use for a hyphen is to join two or more words to create a compound word. A compound word can be a compound adjective, a compound noun, or a compound number.
A compound adjective (a.k.a. compound modifier) is created by joining two or more words that work together to modify the same noun. A compound adjective can be composed of various combinations of adjectives, nouns, quantifiers, and participles, joined by a hyphen to form a single unit.
Adjective + Adjective
1. Join two adjectives with a hyphen to make a compound adjective.
- “Your liver lies in the top-right quadrant of your abdomen.”
- “The ill-fated Titanic sank quickly.”
- “Color photos look so much better than black-and-white photos.”
Adjective + Noun
2. Join an adjective and a noun with a hyphen to form a compound adjective.
- “The firemen were called to a three-alarm fire last night.”
- “She works two part-time jobs and attends college.”
- “We drank only alcohol-free drinks at the party”
Noun + Noun
3. Form a compound adjective by joining two nouns with the conjunction and.
- “Most brick-and-mortar stores also have a website.”
- “Concrete is our company’s bread-and-butter product.”
- “My crazy uncle sports a salt-and-pepper beard.”
Quantifier + Noun
4. You can form a compound adjective by joining a quantifier and a noun with a hyphen.
- “The 100-year storm comes once in a lifetime.”
- “I bought a five-pound sack of potatoes.”
- “The school bus has a 75-person capacity.”
5. You can use a hyphen to form a compound adjective by joining a past or present participle with an adjective, noun, or adverb.
- “Picking cotton is back-breaking work.” (noun + present participle)
- “We get our bread from an old-fashioned bakery.” (adjective + past participle)
- “The patient was a well-nourished male.” (adverb + past participle)
A compound noun is composed of two or more words joined together to function as a single unit to designate a person, place, or thing. Compound nouns can take three different forms: hyphenated, open (separated by a space), or closed (written as a single word). Below are some examples of hyphenated compound nouns:
- Would you pick me up a six-pack? (quantifier + noun)
- I went to see the dentist for a check-up. (noun + preposition)
- That guy is Ridge Forrester, attorney-at-law. (noun + preposition + noun)
- A 12-year-old won the spelling bee. (number + noun + adjective)
Single-word compound verbs
You can use two separate words, such as an adjective and a noun (or a verb), that function as a single word (compound verb) to describe a very specific action. We place a hyphen between these words to eliminate any potential confusion when reading them.
- “Be sure to color-code the electrical wires before disconnecting them.”
- “Use your mouse to double-click the text links on the home page.”
- “We had to air-condition the house last night, as it was too hot to sleep.”
- “I need to water-proof the old shed before we use it for storage.”
However, some compound words will lose their hyphenation over time, as they become more commonplace in speech and writing as seen below.
- “We tried to soundproof the walls of the recording studio.”
- “Our editor will have to proofread your article.”
- “The clerk shortchanged me four dollars.”
If you’re unsure whether to hyphenate a single-word compound verb, look it up in a good dictionary.
1. Generally, we write double-digit numbers in their numerical form (10, 11, 12, etc.), but they can also be written out as words. A hyphen is used to form a compound number when writing in word form double-digit numbers higher than 20 and lower than 100. For example:
- twenty-one (21)
- fifty-five (55)
- ninety-nine (99)
2. We do the same for a hyphenated number if it appears in a compound that’s more than two digits. For example:
- one hundred fifty-five (155)
- five hundred thirty-six (536)
3. If the number has more than three digits, we use commas in the same way as we would for writing it numerically. For example:
- one thousand, two hundred seventy-six (1,276)
- three million, five hundred eighty-six thousand, one hundred twenty-three (3,586,123)
4. Full years are also written this way, except that we don’t use commas. For example:
- “Italian astronomer Galileo Galilei was born in fifteen sixty-four (1564).”
- “The thirty-eighth (38th) parallel was established in nineteen forty-five (1945).”
We use a hyphen when we write a fraction in word form, as well.
- “Our biology class was about one-third (1/3) full on the first day.”
- “We used three-quarters (3/4) of a tank of gas on our drive to the beach.”
Forming compound words with prefixes
We can attach a prefix to the beginning of a word (root word) to change its meaning. Sometimes adding a prefix to a root word can result in a word that is confusing or difficult to read. A hyphen can be used between the prefix and root to clarify the meaning of the new word.
If the last letter of the prefix and the first letter of the root word are the same—which happens mainly with vowels—you can place a hyphen between them to make them easier to read and understand. For example:
- anti-inflammatory (compare to “antiinflammatory”)
- retro-orbital (compare to “retroorbital”)
- re-election (compare to “reelection”)
- re-examine (compare to “reexamine”)
Note: The use of a hyphen for these types of words is a matter of style and ultimately the writer’s decision. It’s not uncommon to see many of these words spelled without the hyphen (as in “reenact“). Consult a good dictionary or follow your school’s or workplace’s style manual if you’re not sure.
When adding a prefix to a root would result in a word that is confusing or awkward to read, we can use a hyphen between them. For example:
- anti-establishment (compare to antiestablishment)
- co-conspirator (compare to coconspirator)
- de-ice (compare to deice)
Remember that using a prefix without a hyphen is also a valid way to spell many of these words, so using a hyphen is often a matter of personal preference.
Creating words with a different meaning
Sometimes adding a prefix (such as re) will create a word that looks like an existing word with a different meaning. We can use a hyphen to avoid potential confusion. For example:
- re-sign (to sign again) compare to resign (to quit)
- re-cover (to cover again) compare to recover (to find again)
With proper nouns and adjectives
Always use a hyphen to attach a prefix to a proper noun or a proper adjective. This is to avoid the awkardness of having a capital letter appear in the middle of a word. For example:
- pro-China (not proChina)
- pre-Civil War (not preCivil War)
NOTE: Some style guides use an en dash instead of a hyphen when a prefix is attached to a proper noun or adjective that is also a compound word, as in the example above. For example:
- pre– Civil War
With self, ex, and all
As with proper nouns and adjectives, we always use a hyphen with the prefixes self, ex, and all. For example:
- self-absorbed (not selfabsorbed)
- ex-wife (not exwife)
- all-consuming (not allconsuming)
The hanging hyphen
A hanging hyphen (also called a suspended hyphen, floating hyphen, or dangling hyphen) is used when a base word is repeated in multiple, consecutive compound words that are connected by or, and, or to. A hyphen is used in place of the base word to avoid redundancy and improve readability. It is usually the last word of the compound that is omitted and leaves the hyphen “hanging” in its place. For example:
- “The difference between pre- and post-war Germany was profound.”
- “I studied late-nineteenth- and early-twentieth-century architecture.”
- “The field trip will include sixth-, seventh-, and eighth-grade students.”
- “My mother- and father-in-law are coming to dinner.”
- “Every citizen should ask him- or herself what they can do for their country.”
NOTE: A hanging hyphen is the only time a hyphen can be followed (or preceded) by a space. Also note in the last example above that a hanging hyphen can be used for a closed compound word (as in “himself”) that would normally not use a hyphen.
Occasionally, the first word of a hyphenated compound word is omitted, and the hyphen is left “hanging” in its place. For example:
- “We all should honor our servicemen and -women who put themselves in harms way.”
- “The family-owned and -operated small businesses have benefited the most from the booming economy.”
Hyphens can be used for some non-grammatical purposes:
Indicating a range of values
Use a hyphen to indicate a range of values, usually dates or numbers. For example:
- “The local post office is open Monday-Friday, from 9:00 AM-5:00 PM.”
- “Please read pages 33-78 of your textbook for tonight’s homework.”
Separating numerical sequences
We can use hyphens to separate long sequences of numbers (non-mathematical in nature) into smaller segments. This makes them easier to read and remember. For example:
- “You may reach me at my business telephone number: 1-800-445-2121.”
- “My social security number is 239-41-3634.”
- “Your customer ID number is 0000-4391-67300B.”
NOTE: Many style guides recommend using an en-dash instead of a hyphen to divide long sequences of numbers as in the above examples. For more information on using en and em dashes, check out our section on Dashes.
When not to use a hyphen
We do not use a hyphen when forming compound words with adverbs that end in “ly” or with the adverb “very,” as it is always understood that they are modifying the adjective or participle that follows them. For example:
- “There are many happily married couples in our group.”
- “We heard a very loud explosion and then saw an extremely bright flash of light.”
Be aware that the above rule does not apply to adjectives or nouns that end in ly—these will take a hyphen in a compound adjective. For example:
- “Oskar Schindler helped Jews escape to ally-controlled countries during World War II.”
- “We all thought she was a sickly-looking kid growing up, but now she appears to be fit as a fiddle.”
Also, we usually don’t use a hyphen with compound adjectives when they follow the noun they are modifying. For example:
- “Your mother seems to be a bit old fashioned.”
- “The newborn infant weighed nine pounds.”
- “The restaurant in our neighborhood is family friendly.”
- “My in-laws can be a bit meddlesome, but they are well intentioned.”
Note that there are exceptions to the above, as certain compound adjectives will always be hyphenated even when they follow the noun they modify. For example:
- “The water in our pool is a beautiful shade of aqua-blue.”
- “I only drink sodas that are sugar-free.”
- “China exports cheap products that are mass-produced.”
If you’re unsure, look up the compound adjective in a good dictionary and see if it is hyphenated. If so, it likely is always hyphenated regardless of its position in the sentence.
Hyphen vs. Dash
Hyphens and dashes are often confused and misused. This is mainly because they are so similar in appearance. They are, however, completely different punctuation marks that have subtle differences in their appearance but major differences in how they should be used to punctuate. For example:
Em dash —
An em dash is twice as long as an em dash and is used to indicate a major break in a sentence.
En dash –
An en dash is shorter than an em dash but longer than a hyphen and is mostly used to indicate a range of numbers.
A hyphen is the shortest and thinnest of these three punctuation marks, and, as we have seen above, its main use is to join compound words.
To see more about how dashes are used, see the dash page.