What is the difference between hemophilia a and hemophilia b?

Hemophilias: Hemophilia is a bleeding disorder, usually inherited with an x-linked recessive inheritance pattern, which results from the deficiency of a coagulation factor. Hemophilia a results from the deficiency of clotting factor viii. Hemophilia b results from the deficiency of clotting factor ix. Acquired hemophilia is a separate noninherited condition, rarer than congenital hemophilia, autoimmune.

Bleeding disorder: Hemophilia a is due to the absence of clotting factor viii (most common) hemophilia b is due to the absence of clotting factor ix (less common).