noun
one daughter; a daughter
Used when counting or referring to having exactly one daughter, often in contrast to having multiple children or no daughters.
彼には一女がいる。
He has one daughter.
noun
eldest daughter; first-born daughter
Refers to the oldest daughter in a family; synonymous with 長女 but more common in formal or written contexts.
See also: 長女
彼の一女は来年大学を卒業する。
His eldest daughter will graduate from university next year.