Knight Bachelor

In the United Kingdom, a Knight Bachelor is a man who is a knight, (has the title Sir) but who is neither a:
 senior member of one of the orders of chivalry, sometimes called orders of knighthood, nor
 a baronet.

In the 1920s, the Society of Knights Bachelor were allowed to wear a special badge on the days when other knights would wear their insignia.

The title is not hereditary, so it cannot be passed on to the knight's children, but a baronet's title can be inherited.

Men who get some jobs, such as senior judges, are made Knights Bachelor. Women cannot be knights bachelor, so if they get one of those jobs, they are made Dames of the Order of the British Empire (DBE)

Knights Bachelor have no post-nominal letters (letters after their name to show they are a knight), unlike knights of the orders of knighthood, who use letters like KBE, or GBE etc., or baronets who put Bt or Bart after their name.

The title "Sir" is always followed by the given name, so, Paul McCartney would be "Sir Paul McCartney" or "Sir Paul". They would never be Sir last name, so not "Sir McCartney". The same applies for women with the title "Dame" ("dame" is pronounced to rhyme with "same").