firstborn

US: /ˈfɝstˈbɔrn/ ,(fûrst′bôrn′)

WordReference Random House Learner's Dictionary of American English © 2025

first•born /ˈfɜrstˈbɔrn/   adj. [before a noun]

1. first in the order of birth;
   eldest:
   the first-born son.

n. [countable* singular;
the + ~]

2. a firstborn child.

WordReference Random House Unabridged Dictionary of American English © 2025

first•born  (fûrst′bôrn′), adj. 

1. first in the order of birth;
   eldest.

n. 

2. a firstborn child.
3. a first result or product.

• 1300–50; Middle English; see first, born

Collins Concise English Dictionary © HarperCollins Publishers::

first-born adjective

1. eldest of the children in a family

noun

1. the eldest child in a family