These letters are abbreviations for the words Peace Be Upon Him which are the meaning of the Arabic expression " 'Alaihis Salam", which is an expression that is said when the name of a prophet is mentioned. This expression is widely used by English speaking Muslims. It is to be noticed here that this expression does not give the full meaning of "Salla Allahu 'Alaihi Wa Sallam". Therefore it is recommended that people do not use (p.b.u.h.) after the name of prophet Muhammad (s.a.w.); they should use "Salla Allahu 'Alaihi Wa Sallam" instead, or they may use the abbreviated form of (s.a..w) in writing.