eighteenth
UK[ˌeɪˈtiːnθ]US[ˌeɪˈtiːnθ]
adj
Constituting number eighteen in a sequence; 18th.
n
The person or thing that is number eighteen in a sequence.
n
One of eighteen equal parts of something.
Morpheme Breakdown
eight
teen
th
eight
number
teen
ten
th
ordinal suffix
Etymology
The word 'eighteenth' is a modern English ordinal number formed through a clear and consistent Germanic pattern. Its first element, 'eight', descends directly from the Proto-Germanic 'ahtōu', which itself originates from the Proto-Indo-European 'oḱtṓw', meaning 'eight'. The '-teen' suffix, meaning 'ten', comes from Old English '-tēne', related to 'tīen' (ten), indicating that the number is eight units beyond ten. Finally, the ordinal suffix '-th', from Old English '-þa', is added to convert the cardinal number 'eighteen' into its ordinal form, 'eighteenth', designating position in a series. This tripartite structure elegantly encapsulates a process of decimal-based counting and sequential ordering fundamental to the English number system.
Analysis
Structure: eight (number) + teen (ten) + th (ordinal suffix)
eight: From Old English 'eahta', meaning the number eight. A cardinal number.
teen: From Old English '-tēne', a suffix meaning 'ten'. It is used to form the numbers thirteen through nineteen.
th: From Old English '-þa', '-þe', an ordinal suffix used to form ordinal numbers from cardinal numbers.
Examples
We are celebrating our eighteenth wedding anniversary this June.
The amendment is famously known as the Eighteenth Amendment, which established Prohibition in the United States.
She inherited one eighteenth of her grandfather's vast estate.