1. coming after the seventeenth in order or position

1. the eighteenth item in a series
2. one of eighteen equal parts of something

Examples

• She celebrated her eighteenth birthday last month.
• The eighteenth century was marked by significant political changes.
• He finished in eighteenth place in the marathon.
• The eighteenth amendment to the Constitution prohibited alcohol.
• Only one eighteenth of the pie remained.
• The meeting is scheduled for the eighteenth of next month.
• Mozart composed many works in the eighteenth century.