The humble hyphen might just be a tiny stroke on a page, but it has the power to change the meaning of a sentence depending on its placement. Hyphens make the distinction, for example, between a ‘wild-animal advocate and a ‘wild animal advocate’. Here’s a primer on when you should (and shouldn’t) hyphenate words.

1. Attributive and predicative compound adjectives

Attributive compounds

‘I thought You Only Live Twice was a really high-quality Bond movie.’

This is an example of an attributive compound adjective. The adjective (which is a compound of two words: ‘high’ and ‘quality’) comes before the noun (‘movie’). Attributive compound adjectives are hyphenated.

Never hyphenate compounds including an adverb (generally, a word ending in ‘ly’), whether attributive or predicative.

So:
• ‘highly efficient system’ not ‘highly-efficient system’
• ‘carefully laid plans’ not ‘carefully-laid plans’.

Predicative compounds
‘The acting, direction, script and plot were terrible, but at least the wardrobe was high quality.’

This is an example of a predicative compound adjective. The adjective (again a compound of ‘high’ and ‘quality’) comes after the noun (‘wardrobe’). Do not hyphenate predicative compound adjectives.

So:
• ‘long-term plan’ vs. ‘a plan for the long term’
• ‘low-rent apartment’ vs. ‘paying low rent’
• ‘full-time employee’ vs. ‘employed full time’
• ‘green-thumb gardening skills’ vs. ‘having a green thumb’.

In some cases, whether or not a compound should be hyphenated is open to debate. For example, noun-plus-adjective compounds should be hyphenated whether they’re attributive or predicative according to many style experts.

So:
• ‘an energy-efficient fan’ and ‘the fan was energy-efficient’
• ‘a cost-effective system’ and ‘a new system which is cost-effective’.

However, strictly adhering to this rule can sometimes seem unnecessary, in phrases such as:
• ‘our restaurants are family-friendly’
• ‘the product is garden-safe’.

In the first set of examples, the compound adjectives are commonly used industry terms which are always hyphenated. In the second set, the hyphens seem a little excessive.

Ultimately, the choice of whether to hyphenate these terms or not comes down to common sense: if it makes sense without a hyphen, leave the hyphen out. If the hyphen would make the sentence clearer, add one in.

2. Hyphenating comparative and superlative compound adjectives

There are a couple (more) things to consider when hyphenating compound adjectives: Is one of the words comparative or superlative? If so, is the other word a participle?

Comparative words include ‘higher’, ‘lower’, ‘faster’ and ‘grumpier’.

Superlative words include ‘best’, ‘worst’, ‘slowest’ and ‘ugliest’.

A participle (in simple terms) is a word based on a verb that’s being used as an adjective. Like ‘growing [pains]’, ‘running [shoes]’ and ‘looking [glass]’.

When a compound adjective comprises a comparative or a superlative and a participle, do not hyphenate. For example:
• ‘fastest growing beanstalk’ (not ‘fastest-growing beanstalk’)
• ‘lower performing company’ (not ‘lower-performing company’)
• ‘grumpiest looking cat’ (not ‘grumpiest-looking cat’).

If the second half of the compound adjective isn’t a participle, do use a hyphen. For example:
• ‘highest-resolution TV screen’ (‘resolution’ isn’t a participle)
• ‘worst-case scenario’ (‘case’ isn’t a participle).

However, we don’t hyphenate those really common or industry-specific phrases like ‘best practice standards’ or ‘lower income earners’.

3. What to do when the compound adjective has more than two words

Use an en dash! For example:
• ‘anti–money laundering regulations’
• ‘new technology–based solutions’.

In the first example, the prefix ‘anti-’ modifies ‘money laundering’, a two-word noun phrase, which in turn modifies ‘regulations’. The en dash connects the three-word phrase ‘anti–money laundering’, to distinguish these regulations from laundering regulations which are anti-money.

In the second example, the en dash falls between the second and third words in the compound adjective to indicate that ‘based’ is modified by the two previous words. This means the phrase reads as ‘solutions based on new technology’ rather than ‘new solutions based on technology’.

4. Hyphenating title case headings

It’s a common misconception that when you hyphenate two words they behave as one word, and so only the first word should be capitalised in a title case heading, product name or similar. This isn’t true of most compound adjectives. Unless the first part is a prefix (such as pre-, anti- or co-), both words should be capitalised the same way.

For example:
• ‘Entering Full-Screen Mode’
• ‘How to Update Your Company’s Back-Office Systems’
• ‘The Benefits of a Managed Co-location Solution’
• ‘Leverage Pre-installed Software’.

In the first two examples, the second part of the compound adjective (‘Screen’ and ‘Office’) starts with an uppercase letter. This is because the adjective is made of two separate words, each of which could stand alone.

In the last two examples, the second word (‘location’ and ‘installs’) is all lowercase. In this case we’re dealing with a prefix and a word, which isn’t really a compound adjective. The hyphen fuses the prefix and the word it is modifying into a single word.

And a final note…
All this is superseded by the rule that if the meaning is unclear, confusing or misleading without a hyphen, add a hyphen! Do you mean ‘more experienced employees’ (more employees with experience) or ‘more-experienced employees’ (employees with more experience)?

Olivia McDowell is one of Editor Group’s dedicated editors and proofreaders. Contact her here.  

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