Meaning of SIR in English

SIR

[sir] n [ME, fr. sire] (13c) 1 a: a man entitled to be addressed as sir--used as a title before the given name of a knight or baronet and formerly sometimes before the given name of a priest b: a man of rank or position

2. a--used as a usu. respectful form of address b cap--used as a conventional form of address in the salutation of a letter

Merriam-Webster English vocab.      Английский словарь Merriam Webster.