Avogadro's Number, also known as Avogadro Constant, is a fundamental physical constant that represents the number of particles in one mole of a substance. This number is usually denoted as 6.022 x 10^23. The term "Avogadro" refers to the Italian physicist and chemist Amedeo Avogadro, who discovered this concept in 1811. There are several synonyms for Avogadro's Number, including Avogadro Constant, Loschmidt's Number, Avogadro's Law Constant, and the Avogadro-Kroegel Constant. These terms are often used interchangeably and are essential in chemistry and physics, helping scientists in determining the number of atoms or molecules in a given substance.