Dear Sir

Daniel recently asked me, “Is it correct to address someone by Sir even in informal contexts such as Instant Messaging or on a blog comment?”

The word sir serves a very useful purpose in English, even in those cultures that cherish democratic ideals to the extreme.

Sir has been used as a respectful form of address in English since about 1350. Its use as a salutation at the beginning of letters can be traced to 1425.

Originally used as a title for a knight, baronet, or (until the Seventeenth Century, a priest), the word sir, like sire, comes from a Latin word related to the word senior and had the meaning “older” or “elder.” Sir is still used to preface a knight’s given name: Now that Rudy Giuliani has been knighted, he can be called “Sir Rudy.”
The form sire, with the sense of “your majesty,” is used to address a king. As a noun in more general use, sire has the meaning “father” or “male parent.” The word can also be used as a verb: John Brown sired several sons.

The most frequent general use of sir is in the context of letter writing, a form of expression that is notoriously conservative in its language. For example, the British complimentary closing “yours faithfully” sounded really abject to my American ear the first time I heard it, but, living in England, I soon became accustomed to it for what it is, a polite convention that no one takes literally.

Outside its conventional use as a written salutation, sir is a convenient word to have in a situation in which one wishes to politely catch the attention of a stranger:

Sir, you’ve dropped your credit card.
Excuse me, Sir, can you direct me to the town center?

The female equivalent in such a situation would be “Miss” or “Ma’am.”

Even in a democracy–perhaps especially in a democracy–the older forms of courtesy are never out of place.