S: (n) principle, rule (a rule or law concerning a natural phenomenon or the function of a complex system) "the principle of the conservation of mass"; "the principle of jet propulsion"; "the right-hand rule for inductive fields"
S: (n) Gresham's Law ((economics) the principle that when two kinds of money having the same denominational value are in circulation the intrinsically more valuable money will be hoarded and the money of lower intrinsic value will circulate more freely until the intrinsically more valuable money is driven out of circulation; bad money drives out good; credited to Sir Thomas Gresham)
S: (n) mass-energy equivalence ((physics) the principle that a measured quantity of mass is equivalent (according to relativity theory) to a measured quantity of energy)
S: (n) Naegele's rule (rule for calculating an expected delivery date; subtract three months from the first day of the last menstrual period and add seven days to that date)
S: (n) principle of equivalence ((physics) the principle that an observer has no way of distinguishing whether his laboratory is in a uniform gravitational field or is in an accelerated frame of reference)
S: (n) principle of superposition, Huygens' principle of superposition (the displacement of any point due to the superposition of wave systems is equal to the sum of the displacements of the individual waves at that point) "the principle of superposition is the basis of the wave theory of light"
S: (n) mass-action principle, mass action ((neurology) the principle that the cortex of the brain operates as a coordinated system with large masses of neural tissue involved in all complex functioning)