noun
Legal and formal term for a child born to unmarried parents. In everyday conversation, 非嫡出子 (ひちゃくしゅつし) or descriptive phrases are more common.
私生子の法的地位は国によって異なる。
The legal status of an illegitimate child varies by country.
彼は私生子として生まれたが、後に父親に認知された。
He was born an illegitimate child, but was later acknowledged by his father.
Historically referred to a child born to a concubine or a non-primary wife, carrying a different social nuance. 私生子 is a broader term for any child born out of wedlock.
Composed of 私 (private, personal) + 生 (birth) + 子 (child). The term is a direct kanji compound meaning 'child of a private (non-marital) birth'. The exact historical origin is uncertain, but it follows a common pattern for formal Sino-Japanese vocabulary.