Compound words

A compound is made up of 2 or more words that together create a new meaning. Compounds can be:

open (‘pay roll’)
hyphenated (‘pay-roll’)
closed (‘payroll’).

Which form a compound takes will depend partly on its function and partly on common usage. Some hyphenation is set by grammatical rules, but in other cases compounds tend to move from open to closed forms over time.

When deciding which form to use, apply the principles below. You can also consult the Macquarie Dictionary to check on the most common usage for a particular compound in Australia.

Open compound words

These are styled as 2 words and often involve an adjective paired with a noun, or an ‘ly’ adverb

real estate

meeting room

newly decorated

Many open compounds combine an adjective with a noun to create a new noun (such as ‘hot dog’). This differs from everyday nouns with a modifying adjective (such as ‘red car’) because they create a new meaning. While a red car is still a car, a hot dog is not literally a dog.

I am concerned about my daughter starting primary school next year because she has a severe allergy to peanut butter.

The second type of open compound pairs adverbs ending in ‘ly’ with a second word. You will occasionally see these constructions hyphenated, but the hyphen is unnecessary because there’s no chance the compound will be misread.

The charity's work is highly regarded and their recent housing program has seen a statistically significant fall in local homelessness.

Hyphenated compound words

Hyphens are most common in compound adjectives when they come before a noun

out-of-pocket expenses

up-to-date records

go-ahead

Compounds most commonly need a hyphen when used as adjectives. Hyphenating these words when they appear before a noun helps to clarify that both parts of the compound modify the noun.

The council has made a long-term commitment to rezone for high-density living under its 10-year strategic plan.

Remember these words might not need hyphens when they are not serving as an adjective to another noun.

The council is committed long term to rezoning for living that is high density under its strategic plan for the next 10 years.

You might also hyphenate compound nouns structured as:

a verb and an adverb
a noun and a prepositional phrase.

I hope to get sign-off from my director tomorrow. We need her go-ahead to start recruitment.

The project manager failed to disclose that the main contractor was his brother-in-law.

To assess whether you need a hyphen, consider whether the phrase could be misinterpreted if you didn’t use one.

Closed compound words

Many compounds close up to 1 word over time

worldwide

bookshop

wellbeing

The trickiest decisions for compounds are when new terms are created and they move from hyphenated to closed forms as we become more familiar with them.

For example, when the ‘pay-roll’ and ‘pay-roll tax’ were first invented, as new and unfamiliar terms they were hyphenated. Now as we are more familiar with them, you will commonly see them as ‘payroll’ and ‘payroll tax’.

As even more time passes, we forget that some words were originally hyphenated, such as the following in bold once were.

The IT team will upgrade all software tomorrow.

As these changes can take years, you will encounter words that are stuck for a time between 2 styles. And different forms might be used in different contexts. For example, the tech world has moved to the closed ‘markup’ for processing languages, while many editors would still opt for the hyphenated ‘mark-up’ to describe their work.

Deciding which form to use is a matter of usage rather than grammar. Select the option that is most common in your context, but be aware that over time most hyphenated compounds of this kind move toward the closed form.

Above all, be consistent in the option you choose. Pick one and move on.