hyphens: compound nouns

A compound noun is simply a compound that functions as a noun. Usually, a compound noun will contain a noun as one of its elements. But that doesn’t have to be the case. For example, sing-along is a compound formed from a verb and an adverb, but it functions as a noun:

• The children enjoyed the sing-along around the campfire.

Follow the guidelines below in using hyphens with compound nouns.

1. 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
2. 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 part:

   • ironworker but structural-iron worker
   • housekeeper but lodging-house keeper
3. 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
4. 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
5. Hyphenate nouns of family relationship formed with great and in-law:
   • mother-in-law
   • great-grandfather

   but

   • foster father
   • half sister
   • stepson
   • godmother