1. being the ordinal number matching the number 80 in a series

1. the ordinal number matching 80; one of 80 equal parts of something

Examples

• She celebrated her eightieth birthday with family and friends.
• The eightieth page of the book contains the final chapter.
• He finished in eightieth place in the marathon.
• One eightieth of the total budget was allocated to marketing.
• The eightieth anniversary of the company was marked with a special event.
• She is the eightieth person to sign up for the class.