An adjective is a word to describe a noun. Sometimes we use a noun to describe another noun. In that case, the first noun “acts as” an adjective.

Adjective/noun: happy boy, clever girl, smart worker

“Noun as adjective”/noun: plastic bottle, glass cover, bird cage

Rules of nouns as adjectives

  • The “noun as adjective” will always come first, the second noun is the subject matter. Once you understand this rule, you will understand the meaning of a sentence.
    1. A race dog is a dog that runs in races
    2. A dog race is a race for dogs
    3. A toy house is a toy in the shape of a house
    4. A house toy is a toy for playing in the house, can be any type of toys
    5. A lighthouse is a beacon
    6. A house light is any lighting unit in the house
  • Just like a real adjective, the “noun as adjective” is invariable. It is usually in the singular form. If there is a plural it is on the real noun only.

Correct Usage

  • Toothbrush/Toothbrushes
  • Plastic bottle/Plastic bottles
  • Bird cage/Bird cages

Incorrect Usage

  • Teethbrush/Teethbrushes
  • Plastics bottle/Plastics bottles
  • Birds cage/Birds cages

  • A few nouns look plural but we usually treat them as singular (e.g. news, billiards, athletics, sports, clothes, accounts). When we use these nouns “as adjectives” they are unchanged:
  • news report/news reports, billiards table/billiards tables, athletics game/athletics games, sports article/sports articles, clothes line/clothes lines, accounts clerk/accounts clerks
  • Writing “nouns as adjectives”

We write the “noun as adjective” with the real noun in 3 different ways:

  1. In two separate words (apple pie)
  2. In two hyphenated words (tax-plan)
  3. In one word (football)

There is no fixed rule for this. We sometimes use all the three different ways to write on single “noun as adjective” e.g. head master, head-master, headmaster

The rules of style that apply to dashes and hyphens have evolved to support ease of reading in complex constructions; editors often accept deviations from them that will support, rather than hinder, ease of reading.

  • Saying “nouns as adjectives”

We always emphasize on the first noun that is the “noun in adjective” when speaking.

  • More than one “nouns as adjectives”

We can use more than one “noun as adjectives” to describe a noun, just like we do in adjectives e.g China team badminton coach”

  • Combined “ nouns as adjectives” with adjectives

We can also combine adjective with “noun as adjective” to better describe a noun e.g. “the cute Italian football player”