Certain categories of compound words follow their own rules.
Compass directions
Set simple compass directions solid:
and complex directions with a hyphen:
When ‘from’ and ‘to’ are implied in the sentence, use an en dash:
Age terms
Use the following forms:
but
a child who is 5 years old
Numbers expressed in words
Hyphenate numbers between 21 and 99 expressed in words:
Fractions expressed in words
Hyphenate simple fractions expressed in words:
Expressions of quantities with units
Do not use a hyphen when the unit is abbreviated, but use a hyphen when the unit is spelled out in full:
a 20 L container a 20-litre container
the 100 m race the 100-metre race
Chemical names
Use a hyphen to set off numerals used as locants within a chemical name (see Chemical compounds):
2-hydroxymethyl-1-methyl-5-nitroimadazole 2,4,5-T
Proper nouns relating to geography
Use a hyphen in compound adjectives relating to geography where the first term is a prefix:
but use an en dash where the components have equal weight:
Phrases with italics, capital letters, quotation marks or numbers
Do not hyphenate phrases set in italics, in quote marks, with capital letters or containing numbers:
Foreign phrases
Do not hyphenate foreign phrases that consist of more than 1 word:
Colours
Describing shades of colour with the available words for colour can be difficult. Writers on fashion, decor and architecture, as well as scientists (e.g. botanists, entomologists), may use established compound terms or invent ones to express the colours of the objects they are describing.
Follow these key principles for writing compound colour names.
Do not hyphenate compound colour names that have a long history of use:
For colour combinations in which each colour has equal weight, use an en dash:
The curtains are printed with a yellow–brown pattern.
Grey–green larvae hatch from the insect’s eggs.
Blue–green algae produce toxins that can harm animals.
For compound adjectives that include colours with modifiers based on other colours (e.g. creamy, bluish, reddish), or on shade or intensity (e.g. pale, dull, dark, light, deep):
- include a hyphen when used before the noun they modify
Creamy-white armchairs lighten the tone of the room.
A dark-brown carpet made the room appear gloomy.
The defining symptom of rust is the presence of tan-to-dark-brown or reddish-brown spots on the leaves.
We gazed for hours at the deep-blue sea.
- do not hyphenate when used after the noun they modify
Leaves are bluish green.
Larvae are initially creamy white but develop black marks.
When words just won’t do …
The guesswork can be taken out of colour descriptions by quoting the relevant Pantone® colour. The Pantone Colour Matching System (PMS) is a standardised colour reproduction system. Pantone colour guides(Opens in a new tab/window) are used worldwide for accurate colour identification and design specification.
Considering the complexity of describing colours in words, in some cases it might be more accurate to use Pantone colours when describing individual colour shades or ranges of colour.