Sir

Sir is an honorary title.

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It derives from the Middle English sire, from the French sieur, meaning "lord," from the Latin adjective senior ("elder"), which yielded titles of respect in many European languages

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It was once used (without the person's name) as a courtesy title among equals, but is now usually reserved for one of superior rank or stature (e.g. an educator, chief, ) or in age (especially by a minor); as a form of address from a merchant to a customer; in formal correspondence (Dear Sir, Right Reverend Sir); or to a stranger (Sir, you've dropped your hat).

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The equivalent for a woman is madam.

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