sir, Sir strong form BrE AmE sɜː AmE sɝː , weak form sə AmE s ə r —The weak form is customary in British English whenever this word is used with a name, as Sir John; Sir Peter Smith . Otherwise the strong form is usual: yes, sir . In American English the weak form is little used.
▷ sirs sɜːz AmE \ sɝːz —There is no weak form of the plural.