Gabrielle Émilie Le Tonnelier de Breteuil, Marquise du Châtelet was a French natural philosopher, mathematician, physicist, and author during the early 1730s until her untimely death due to childbirth in 1749. Her most recognized achievement is her translation of and commentary on Isaac Newton's book Principia containing basic laws of physics. The translation, published posthumously in 1759, is still considered the standard French translation today. Her commentary includes a profound contribution to Newtonian mechanics—the postulate of an additional conservation law for total energy, of which kinetic energy of motion is one element. This led to her conceptualization of energy as such, and to derive its quantitative relationships to the mass and velocity of an object.
