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彼は三人の息子がいます。
He has three sons.
A male child in relation to his parents.
息子が医者になりました。
My son became a doctor.
Used for one's own male child; for addressing others' sons, use ご子息 (polite).
Remember 'musuko' as 'moo-soo-ko' with equal stress on all syllables. The 'u' is short, like in 'put'.
息子 strictly means 'son' (male child). For 'child' in general, use '子供' (kodomo).
From Old Japanese 'musuko' (息子), combining '息' (breath/life) and '子' (child), originally implying 'one's breath' as a cherished child.
Commonly used in everyday speech. In formal contexts, ご子息 (goshisoku) is preferred when referring to someone else's son.