Hyphens and dashes

Hyphens are used to link words and parts of words.

Three main uses of the hyphen

1. in compound words
2. to join prefixes to other words
3. to show word breaks 

1. Hyphens in compound words

Hyphens are used in many compound words to show a combined meaning:

EXAMPLE:  a pick-me-up, mother-in-law, good-hearted 

Hyphens also show that there is a relationship between the words that make up the compound:

EXAMPLE: rock-forming minerals are minerals that form rocks.

But you do not need to use them in every type of compound word.

Compound adjectives

Compound adjectives are made up of a noun + an adjective, a noun + a participle, or an adjective + a participle.

Many compound adjectives should be hyphenated. 

EXAMPLES:

Use a hyphen with compound adjectives formed from the adverb well and a participle:

EXAMPLE: well-known

Use a hyphen with compound adjectives formed from a phrase:

EXAMPLE: up-to-date

Use a hyphen with compound adjectives formed when the compound comes before the noun:

EXAMPLE: well-known brands of coffee

But do not use the hyphen when the compound comes after the noun:

EXAMPLE: His music was also well known in England.

EXAMPLE: Their figures are up to date.

It is important to use hyphens in compound adjectives describing ages and lengths of time: leaving them out can make the meaning ambiguous.

EXAMPLE: 250-year-old trees (clearly refers to trees that are 250 years old, while 250 year old trees might also refer to 250 trees that are all one year old)

Compound verbs

Use a hyphen when a compound formed from two nouns is made into a verb, for example:

 EXAMPLES:

Phrasal verbs

You should NOT put a hyphen within phrasal verbs, i.e. verbs made up of a main verb and an adverb or preposition:

EXAMPLES:

If a phrasal verb is made into a noun, though, you SHOULD use a hyphen:

 EXAMPLES:

Compound nouns

A compound noun is one noun consisting of two components. In principle, such nouns can be written in one of three different ways, so be prepared to see all of these different ways of writing compound nouns in your reading of various English texts.

 EXAMPLES:

use two words to form a compound noun

We, at UT, recommend you use two words to form compound nouns:

EXAMPLE: boot camp

However, the most important thing to note is that you should choose one style and stick to it within a piece of writing:

AVOID:  bootcamp in one paragraph and then boot camp in another

2. Hyphens joining prefixes to other words

Hyphens can be used to join a prefix to another word, especially if the prefix ends in a vowel and the other word also begins with one:

EXAMPLE: pre-eminent or co-own

Use a hyphen to separate a prefix from a name or date:

EXAMPLE: post-Aristotelian or pre-1900

Use a hyphen to avoid confusion with another word:

EXAMPLE: to distinguish re-cover (= provide something with a new cover) from recover (= get well again).

3. Hyphens showing word breaks

Hyphens can also be used to divide words that are not usually hyphenated. They show where a word is to be divided at the end of a line of writing. Always try to split the word in a sensible place, so that the first part does not mislead the reader:

EXAMPLE: hel-met 

AVOID: he-lmet

Hyphens are also used to stand for a common second element in all but the last word of a list:

EXAMPLE: You may see a yield that is two-, three-, or fourfold.

The em dash, or long dash (–)

An em dash, or long dash, is used for two reasons:

 1. to mark off information or ideas that are not essential to an understanding of the rest of the sentence (use a pair of dashes):

EXAMPLE: Thousands of children—like the girl in this photograph—have been left homeless.

2. to show other kinds of break in a sentence where a comma, semicolon, or colon would be traditionally used:

EXAMPLE: One thing’s for sure—he doesn’t want to face the truth.

EXAMPLE: Things have changed a lot in the last year—mainly for the better.

Note that there is no space added on either side of an em dash.

Em dashes are especially common in informal writing, such as personal emails or blogs, but it’s best to use them sparingly when you are writing formally.

The en dash, or short dash (–)

The en dash is slightly longer than the hyphen but not as long as the em dash (it is, in fact, the width of a typesetter’s letter “N,” whereas the em dash is the width of the letter “M”—thus their names). The en dash means, quite simply, 'through.'

We use it most commonly to indicate inclusive dates and numbers:

EXAMPLE: July 9–August 17; pp. 37–59.

Note that there is no space added on either side of an en dash.

Typing the em dash 

The em dash can be typed as Alt + 0151.

Typing the en dash

The en dash can be typed as Alt + 0150.

References and further tips 

• Oxford Dictionaries Blog. 'How to use hyphens'. Retrieved from https://blog.oxforddictionaries.com/2011/10/11/hyphens-in-the-headlines/
• Get it Write. 'En Dashes and Em Dashes'. Retrieved from https://getitwriteonline.com/articles/en-dashes-em-dashes/ 
• Oxford Living. 'punctuation/hyphen' Retrieved from https://en.oxforddictionaries.com/punctuation/hyphen