Philosophiæ Naturalis Principia Mathematica

Isaac Newton’s 1687 treatise established the laws of motion and universal gravitation, applying them to explain the motions of celestial and terrestrial bodies.

Newton's laws of motion: Three laws relating bodies’ motion to inertia, applied force, and equal-and-opposite interactions. They provide the treatise’s basic rules for translating forces into motion.
Inertia: The tendency of a body to maintain its state of rest or uniform straight-line motion unless acted on by a force. Newton’s first law recasts inertia as the baseline state from which forces alter motion.
Edmond Halley: An English astronomer who helped publish Newton’s Principia and studied the comet later named after him. Halley prompted Newton to develop his orbital argument and paid to publish the first edition.
Celestial mechanics: The mathematical study of the motion of celestial bodies under gravitational forces. The Principia established a framework for calculating planetary and cometary motion.
Newton's law of universal gravitation: A law stating that every pair of masses attracts with force proportional to their product and inversely proportional to distance squared. It extends terrestrial gravity to the Moon, planets, and other celestial bodies.
Force: An interaction that changes a body's motion or tends to change it. Newton makes force mathematically comparable to changes in motion.
Robert Hooke: An English natural philosopher who proposed an inverse-square gravitational attraction and disputed priority with Newton. Their correspondence and later dispute formed part of the treatise’s intellectual background.
Newtonian mechanics: The classical theory of motion based on Newton’s laws and force-based dynamics. The treatise became the foundational presentation of this mechanics.
Kepler's laws of planetary motion: Three empirical rules describing planetary orbits, orbital areas, and periods around the Sun. Newton derived these orbital regularities from his laws and gravitational force.
Momentum: A body's mass multiplied by its velocity, a quantity changed by applied force. Newton’s laws describe force through changes in this quantity.

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