eighteenth

eighteenth — adjective

1. coming after the seventeenth item in a series of things that are arranged or cou

1.adjectiveA1
Definition

coming after the seventeenth item in a series of things that are arranged or counted; written as the word '18th' when showing position in dates, lists, or rankings.

Example

Quinn celebrated his eighteenth birthday with a small family dinner.

collocation: eighteenth birthday

The eighteenth chapter of the novel finally reveals the killer.

Common collocations
  • eighteenth birthday
  • eighteenth century
  • eighteenth chapter
  • eighteenth place
  • eighteenth year

Grammar Patterns

the eighteenth + noun

possessive + eighteenth + noun

Usage Note

Ordinal numbers such as 'eighteenth' always go before the noun they describe. Do not use 'eighteenth' after cardinal numbers: ❌ 'Chapter eighteenth' ✅ 'the eighteenth chapter.'

Common Mistakes

Her eighteenths birthday
Her eighteenth birthday
ordinals do not take -s for plural; 'eighteenth' stays singular before a noun.
She came at eighteenth place
She came in eighteenth place
the correct preposition before a ranking position is 'in', not 'at'.

eighteenth — noun

Word family

  • eighteen
    numberA1
  • eighteen-year-old
    adjectiveA2
  • eighteen-year-old
    nounA2

Synonym discussion

Sense: adjective/1

The ordinal 'eighteenth' (or its numeric form '18th') refers to position in a sequence, while the cardinal number 'eighteen' refers to a quantity. Use 'eighteenth' when you want to show where something falls in an order: 'the eighteenth floor', 'her eighteenth birthday.' Use 'eighteen' to talk about the number itself: 'eighteen people attended.' The numeric form '18th' is common in informal writing, addresses, and dates ('July 18th'), while 'eighteenth' is preferred in formal prose ('the eighteenth century'). Avoid mixing forms: do not write 'the 18th century' in academic essays where the style guide recommends spelling out ordinals.

eighteenth ↗18theighteen ↗

Common collocations

Nouns

Phrases

  • the eighteenth of [month]
  • [month] eighteenth
  • the eighteenth to [verb]

Prepositions

  • in eighteenth
  • on the eighteenth
  • of the eighteenth

Etymology

Old EnglishMiddle EnglishEnglish

'Eighteenth' comes from Old English 'eahtatēoþa', a combination of 'eahta' (eight) and 'tēoþa' (tenth). The word evolved through Middle English 'eightetethe' before settling into the modern form 'eighteenth'. It follows the same pattern as other teen ordinals (thirteenth through nineteenth), where the suffix '-teenth' attaches to the cardinal number and indicates position in a series.