sir

Sir is a formal honorific used in the English language primarily as a title for male knights and baronets, and more generally as a courteous form of address for men in formal or respectful contexts.

Originating from the Old French sire, itself from Latin senior meaning elder, the word historically referred to lords or kings. In medieval English, sire was used to address a sovereign, while sir developed as a title for knights and later for baronets. Over time, sir became the standard pre-nominal for male knights in many English-speaking societies.

In modern usage, Sir precedes the holder's given name or full name, as in Sir Ian McKellen. It is conferred through knighthoods and baronetcies, and recipients may be addressed as "Sir" alone in direct speech or "Sir X" in conversation. In written correspondence, "Dear Sir" is a traditional salutation when the gender of the recipient is unknown; specific recipients are addressed by title and surname. The female equivalent is Dame.

In royal usage, Sire is the form of address for a king or male sovereign and is typically not used for knights. In many countries, including those of the Commonwealth, Sir remains a conventional title, though not all men who are addressed as Sir are necessarily knights; some orders may use the title for certain officials.