modulus: (physics) a coefficient that expresses how much of a specified property is possessed by a specified substance
definite quantity: a specific measure of amount
rheumatoid arthritis: a chronic autoimmune disease with inflammation of the joints and marked deformities; something (possibly a virus) triggers an attack on the synovium by the immune system, which releases cytokines that stimulate an inflammatory reaction that can lead to the destruction of all components of the joint