the ordinal number matching the number 1011; coming after the tenth and before the twelfth in a series.
From eleven plus -tenth (the ordinal suffix). Old English endleofan became 'eleven,' and -teenth indicates position in sequence from 13-19.
The eleventeenth is rare to use in everyday English because we usually stop at 'tenth' before jumping to 'twentieth,' making it one of the weirdest numbers to say out loud.
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