The description of the word you requested from the astronomical dictionary is given below.
Isaac Newton (1662 - 1727) was the founder of the science of mechanics. Newton gave the first useful explanation of gravity, in the form of Newton's Law of Gravity. With this he explained how the Moon orbits the Earth. Newton also invented differential calculus and explained many optical phenomena such as the spectrum. The unit of force is named newton (symbol: N) after him.
The three "ordinary" Laws of Newton are: