eightteenth

Eightteenth is not a standard English word. The correct ordinal for the number eighteen is eighteenth. The form eightteenth, while occasionally seen in informal writing or as a misspelling, is regarded as nonstandard.

Morphology and origin: The ordinal for eighteen is formed by taking the cardinal eighteen and adding the ordinal suffix -th, yielding eighteenth. This follows the common pattern for numbers in the teens and for numbers ending in -teen, where the base ends with -teen before the final -th is appended (for example, thirteenth, fourteenth, sixteenth, eighteenth, nineteenth, etc.). The cardinal eight, by contrast, forms the separate ordinal eighth, not eightteenth.

Usage: In formal writing and standard references, you should write eighteenth when referring to the ordinal position associated with the number 18, for example, “the eighteenth century” or “she finished eighteenth in the race.” When numbers are written numerically, you would use 18th. The form eightieth denotes the 80th position, showing that unrelated ordinal formations can arise from different numeric bases.

Notes: Some style guides note eightteenth as a common error and advise writers to prefer eighteenth. Contexts such as dictionaries, style manuals, and editorial practices typically treat eighteenth as the accepted form. For clarity, maintain consistency in your text by using eighteenth for eighteen-based ordinals and eighteenth-century usage as a standard example.