noun
Formal or written term for a male child, often used in news reports, statistics, or official contexts. Contrasts with 女児 (girl).
See also: 女児
事故で男児が軽傷を負った。
A boy suffered minor injuries in the accident.
彼は三人の男児の父親だ。
He is the father of three sons.
noun
Rare, formal, and somewhat old-fashioned when used for an adult male. More commonly encountered in set phrases or historical contexts.
男児たるもの、一度決めたことは最後までやり通せ。
A man should see through what he has decided.
男の子 is the standard, casual word for a boy, while 男児 is formal and often used in writing or news.
Compound of 男 (dan, 'male') and 児 (ji, 'child'). The kanji 児 is a common suffix in formal terms for children, as in 幼児 (young child) or 胎児 (fetus).