Humble term used to refer to one's own son when speaking to someone outside the family. Not used for other people's sons.
My son is getting married next month.
My son is still a university student.
young punk; brat
Derogatory or dismissive term for a young man, often implying inexperience or cheekiness. Can be used for someone else's son in a critical tone.
That brat has no manners.
The neighborhood punk is so noisy it's a problem.
Vulgar slang; used colloquially to refer to the male organ. Not appropriate in polite conversation.
Stop bringing up penis jokes with that crude humor.
I introduced my son to our business partner.
Don't talk back to me, you cheeky brat.
息子 is the neutral, everyday word for 'son' usable for anyone's child, while せがれ is a humble term used only for one's own son (or a derogatory one for someone else's).
坊主 is a broader, casual term for a young boy or kid, whereas せがれ specifically implies 'son' with a dismissive or humble edge depending on context.
my son; one's own son · you little brat; you little bastard
Usually written in kana; the kanji forms 倅, 伜, 悴, 忰 are rare and mostly encountered in older texts.
Rare kanji form; may appear in literary or historical contexts.
Rare variant kanji form.
Rarely used kanji form.
Rarely used kanji form.
The origin is uncertain. It may derive from 背 (se, 'back' or 'height') + が + れ, but the exact derivation is unclear. The kanji forms are ateji.