eighteenth

IPA/ˌeɪˈtiːnθ/
KK[etˈinθ]IPA/ˌeɪˈtiːnθ/

eighteenth — number

1. the word for the number 18 when you are counting or describing the position of s

1.numberB1
Definition

the word for the number 18 when you are counting or describing the position of something in a list, series, or sequence — for example, the eighteenth person to arrive, or the eighteenth floor of a building.

Example

Nikos celebrated his eighteenth birthday with a trip to the Greek islands.

ordinal before noun: eighteenth + birthday

The eighteenth chapter of the history book covers the end of the war.

the eighteenth + noun

Common collocations
  • eighteenth birthday
  • eighteenth century
  • eighteenth floor
  • eighteenth year
  • eighteenth time
  • eighteenth place

Grammar Patterns

the eighteenth + noun

the eighteenth to + verb

eighteenth + noun (no article in some contexts)

Usage Note

When used with a date, 'the eighteenth' is the usual way to say the 18th day of a month (e.g., 'the eighteenth of May'). The ordinal form is also used in titles of rulers (Henry VIII is read as 'Henry the Eighth', following the same pattern for eighteen).

Common Mistakes

She is eighteen years old on her eighteen birthday.
She is eighteen years old on her eighteenth birthday.
Ordinal numbers (eighteenth) mark position in a series; cardinal numbers (eighteen) mark quantity.
We are meeting on eighteen June.
We are meeting on the eighteenth of June.
Dates in English use the ordinal form.

eighteenth — noun

eighteenth — adjective

Word family

  • eight
    numberA1
  • eighteen
    numberA1
  • eighth
    numberA2
  • eighty
    numberA2
  • eightieth
    numberB2

Synonym discussion

Sense: adjective/1

'Eighteen' (A1) is the cardinal number — it tells you how many there are ('eighteen students in the class'). 'Eighteenth' (B1) is the ordinal form — it shows position in a sequence ('the eighteenth student in the row'). 'Eight' is a different number entirely and shares only the root. Learners often use the cardinal where the ordinal is needed, especially with dates ('May eighteen' instead of 'May the eighteenth'). If you are talking about order, rank, or sequence, you need the ordinal (eighteenth). If you are counting a total quantity, you need the cardinal (eighteen). A good test: if you can replace the word with 'last' or 'first' and the sentence still makes sense, you need 'eighteenth'. If you can replace it with 'the same number as' or 'as many as', you need 'eighteen'.

eighteentheighteeneight

Common collocations

Nouns

  • birthday
  • century
  • floor
  • anniversary
  • chapter
  • place
  • position

Phrases

  • the eighteenth of
  • one eighteenth of
  • in eighteenth place

Etymology

Old EnglishMiddle EnglishEnglish

'Eighteenth' comes from the Old English word 'eahtatēoða', which was a combination of 'eahta' (eight) and 'tēoða' (tenth). Over time, the word changed through Middle English forms like 'eightetethe' and 'eightenthe' before settling into its modern spelling. The '-th' ending is the standard ordinal suffix in English, added to 'eighteen' (which itself combines 'eight' + '-teen', a suffix meaning 'ten'). The same pattern appears in other ordinals: sixth, seventh, eighth, ninth, tenth, eleventh, and so on.