1. oldest among three or more people, especially children in a family
Usage: used with family members

1. the oldest child in a family
Usage: often used with ‘the’

Examples

• My eldest sister is twenty-five years old.
• The eldest son inherited the family business.
• She is the eldest of four children.
• The eldest in our family always gets the biggest bedroom.
• Their eldest daughter just graduated from college.
• As the eldest, he felt responsible for his younger siblings.