eighteen

eighteen — noun

1. the number 18, used to say how many people or things there are — for example, ei

1.nounA1
Definition

the number 18, used to say how many people or things there are — for example, eighteen students in a class or eighteen dollars in a wallet.

Example

Alessia invited eighteen people to her birthday party.

eighteen + plural noun (people)

The suitcase could hold up to eighteen shirts and a pair of shoes.

eighteen as determiner before a concrete noun

Common collocations
  • eighteen people
  • eighteen years
  • eighteen dollars
  • eighteen students

Grammar Patterns

eighteen + plural noun

2. the number 18, thought of as a symbol or numeral, or someone's age when they rea

2.nounA1
Definition

the number 18, thought of as a symbol or numeral, or someone's age when they reach their eighteenth birthday.

Example

Adina will turn eighteen next Friday after the school play.

turn + eighteen (age expression)

Eighteen is the number of holes on a standard golf course.

Eighteen as subject of a clause

Common collocations
  • turn eighteen
  • over eighteen
  • under eighteen
  • age of eighteen
Synonyms
  • 18

    the digit form, common in informal writing, signs, and forms

Grammar Patterns

be + eighteen (for age)

the number eighteen

Usage Note

Turn eighteen is a fixed expression meaning 'to reach the age of eighteen', often associated with gaining legal rights such as voting or driving.

Common Mistakes

❗ 'I am eighteen years.' ✅ 'I am eighteen years old.' — 'years old' or 'years of age' is needed when using the noun 'years' to describe age.

Word family

Synonym discussion

Sense: noun/2

While 'eighteen' (noun) can refer either to the numeral or the age, '18' is the digit form often used in signs, forms, or informal writing ('students aged 18 and over'). 'The age of eighteen' and 'eighteen years old' are more formal and specific to age, used in legal or official contexts ('Drivers must be eighteen years old'). In everyday speech, 'eighteen' alone is most common for age ('She's eighteen'). For the numeral, 'eighteen' is the standard written form in essays and reports, while '18' is used in tables, addresses, or informal notes.

18the age of eighteeneighteen years old

Common collocations

Phrases

  • over eighteen
  • under eighteen
  • about eighteen

Etymology

Old EnglishEnglish

Eighteen comes from Old English 'eahtatēne', a combination of 'eahta' (eight) and 'tēn' (ten). This pattern of combining the unit with the word for ten is shared across Germanic languages and mirrors how the number is built in everyday counting.