2.02 Compound nouns and nouns in compounds

(a) Hyphenate two nouns representing different but equally important functions, i.e. where the hyphen denotes the relationship "both A and B":

• city-state
• comedy-ballet
• dinner-dance
• soldier-statesman
• tractor-trailer
• writer-editor

(b) Hyphenate nouns normally written as two words, when they have a modifier and when ambiguity would otherwise result:

• colour filter but red colour-filter
• letter writers but public letter-writers

Similarly, compound nouns normally written as a single word must be separated into their component parts and then joined to their modifier by a hyphen when the modifier applies only to the first component:

• ironworker but structural-iron worker
• housekeeper but lodging-house keeper

(c) Hyphenate compound units of measurement made by combining single units that stand in a mathematical relationship to each other:

• car-miles
• kilowatt-hours
• light-year
• person-day

(d) Hyphenate compounds that include a finite verb:

• a has-been
• a stay-at-home
• a sing-along
• a stick-in-the-mud
• a Johnny-come-lately
• a ne’er-do-well

(e) Hyphenate nouns of family relationship formed with great and in-law:

• mother-in-law
• great-grandfather

but

• foster father
• half sister
• stepson
• godmother

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