noun
Standard word for one's own son or someone else's son. Neutral and widely used.
息子は今年大学を卒業します。
My son will graduate from university this year.
彼女の息子さんはとても礼儀正しい。
Her son is very polite.
noun
Colloquial and somewhat vulgar slang. Used mainly among men in casual contexts.
あの冗談は息子の話ばかりで下品だった。
That joke was crude, full of penis talk.