The Collaborative International Dictionary of English v.0.48:
Conservation \Con`ser*va"tion\, n. [L. conservatio: cf. F.
The act of preserving, guarding, or protecting; the keeping
(of a thing) in a safe or entire state; preservation.
A step necessary for the conservation of Protestantism.
A state without the means of some change is without the
means of its conservation. --Burke.
Conservation of areas (Astron.), the principle that the
radius vector drawn from a planet to the sun sweeps over
equal areas in equal times.
Conservation of energy, or Conservation of force (Mech.),
the principle that the total energy of any material system
is a quantity which can neither be increased nor
diminished by any action between the parts of the system,
though it may be transformed into any of the forms of
which energy is susceptible. --Clerk Maxwell.