an equation containing differentials of a function

the result of mathematical differentiation; the instantaneous change of one quantity relative to another; df(x)/dx

a quality that differentiates between similar things

a bevel gear that permits rotation of two shafts at different speeds; used on the rear axle of automobiles to allow wheels to rotate at different speeds on curves

a mathematical statement that two expressions are equal

the act of regarding as equal

a state of being essentially equal or equivalent; equally balanced