What is a Hyphen?
A hyphen is a small horizontal line used to combine two or more words to form a compound word. Hyphens are often confused with em dashes and en dashes. The differences between the three are as follows:
Hyphen (-):
- The hyphen is the smallest of the three in length.
- It is used to create compound words by combining two or more words.
Example: “I’m a mother of a seven-month-old infant,” said Sandra.
En dash (–):
- An en dash is longer than a hyphen but shorter than an em dash. It has the same width as the letter “N” and is therefore called as such.
- It is used to represent a range (from–to) in the case of page numbers, months, time, etc.
Example: “Refer to pages 56–78 in your textbook if you have doubts while working on your assignment,” said the professor to her students.
Em dash (—):
- Em dash is the longest of the three dashes and has the same width as the letter “M” and is therefore called as such.
- It is used to signify a pause and can be employed in place of colons, semicolons, commas, parentheses, etc.
Example: After receiving the bouquets—all 31 of them—she wasn’t sure where to keep them.
Note: A hyphen should not be used interchangeably with either an en or em dash.
Rules for Hyphen Use
Hyphens, like commas, periods, em dashes, and colons, are commonly used punctuation marks. Below are some rules that should be followed while using them:
Rule 1: Hyphens should be used in spelled-out numbers.
All numbers, when spelled out, are compound words. Therefore, twenty-one through ninety-nine should be hyphenated.
Examples:
- There are seventy-five apples in the basket.
- She was on page thirty-three when she fell asleep.
Rule 2: Hyphens should be used in compound adjectives.
If an adjective is composed of two or more words, then it is called a compound adjective. Hyphens should be used only in this type of adjective.
Examples:
- Jacob was a good-looking man who got along well with everyone at the office.
- Jane’s folks are rather broad-minded and modern.
Note: Adjectives that are not compound adjectives should not be hyphenated. If there is more than one adjective used to describe something, then such adjectives should be separated by commas.
Examples:
- Jacob was a good, generous man who got along well with everyone at the office. (Note that there is no hyphen between friendly and generous).
- Jane is a kind, brave woman just like her mother.
Following are some examples of compound adjectives:
- Ice-cold
- Sky-blue
- Deep-fried
- Self-explanatory
- Narrow-minded
- Strong-willed
- Kind-hearted
- Part-time
- Quick-witted
- Well-known
- Sun-dried
- Middle-aged
Rule 3: A hyphen should be used when two words are used as one compound word.
When two or more words are joined to make one word, such a word is called a compound word. Whether the compound word is a verb, adjective, or any other type of word, using a hyphen is imperative to avoid confusion.
Examples:
- They wondered if it was a good idea to sky-dive on a windy day.
- She decided to freeze-dry the extra peas so that she could use them later.
Rule 4: Hyphens should be used while spelling out fractions.
When a fraction is spelled out, it should be hyphenated.
Examples:
- More than two-thirds of the senators voted against the defense bill.
- My grandma’s recipe requires one-half of a cup of flour to make the cake firm.
Rule 5: Hyphens should be used in confusing words.
A hyphen should be used to separate words that can cause confusion or ambiguity.
Examples:
- Instead of writing “Tigers are the most furious of all man eating mammals,” it is better to write “Tigers are the most furious of all man-eating mammals.”
- Instead of writing “Portsmouth in New Hampshire has that quintessential small town charm,” it is better to write “Portsmouth in New Hampshire has that quintessential small-town charm.”
Rule 6: Hyphens should be used with measuring units.
A hyphen should be used before measuring units such as grams, kilograms, pounds, etc. when such units are spelled out.
Examples:
- They decided to go with a 50-pound cake for their wedding.
- She saw a 15-centimeter-long earthworm.
Rule 7: Hyphens should be used in prefixes and suffixes.
7a. Prefixes:
A hyphen should be used:
- After prefixes like “ex,” “self,” “cross,” “all.” (Examples: “ex-girlfriend,” “self-serving,” “cross-examination, ” “all-encompassing”)
- To differentiate words that have the same spelling but different meanings. (Examples: resign vs. re-sign, recovered vs. re-covered, resent vs. re-sent)
- If a prefix ends with a vowel and the word that follows the prefix begins with the same vowel. (Examples: meta–analysis, anti–incumbency, re–elect, co–occur)
- In proper nouns that have prefixes. (Examples: trans-Atlantic flight, pan-American highway, mid-March festival)
7b. Suffixes:
A hyphen should be used:
- If a suffix begins with a particular letter and the word that precedes it ends with the same letter. (Examples: petal–like pattern, shell–like design, metal–like texture)
- In nouns that have suffixes (Examples: restaurant-style fries, BPA-free products, metal-based nanoparticles)
Rule 8: Hyphens should be used in chemical names and formulas.
Hyphens must be used in the names of chemical substances and their formulas.
Examples:
- 2-methylpentane
- (CH₃)₂CH-O-CH(CH₃)₂ (2-propoxy-1-propane)
- Carbon-12
- Carbon-14
Besides the above uses, hyphens are also used to break a word if it doesn’t fit at the end of a line. Although hyphen usage can seem complicated, knowing the rules definitely helps.
