A male child in relation to his parents; son.
うちの息子は来年中学生になります。
Our son will become a junior high school student next year.
息子に大学の受験勉強を手伝ってもらった。
My son helped me with my university entrance exam studies.
彼は一人息子なので、両親が心配している。
He is an only son, so his parents are worried.
Colloquially, can be used as a slang term for the penis (informal usage).
辞書には普通『息子』は子供を意味するとあるが、俗語で別の意味になることもある。
Dictionaries list '息子' as meaning a child, but in slang it can have another meaning.