Refers to a legally adopted child, historically often a male heir or a son-in-law adopted into the family to carry on the name. In modern usage, it can refer to any adopted child, but the traditional association with a male heir or son-in-law remains strong.
He was raised as an adopted child.
昔は、家を継ぐために養子を迎えることが多かった。
In the past, it was common to adopt a child to carry on the family line.
The couple adopted an orphan as their child.
He became his uncle's adopted son.
Childless couples often take in an adopted child as an heir.
deathbed adoption of a successor; person adopted on someone's deathbed
adoption (of a person)