- noun a large amount or number of something
- noun a measure of quantity applied to plants or animals, often based on density or frequency
- The relative amount of a particular type of star, galaxy, atom or other item in an overall population. Elemental abundances, the amounts of different atomic species in meteorites, moonrock etc, yield information about the early history of the solar system. The abundances of different types and ages of stars in the galaxy tells us about the evolution of both stars and galaxies. Stellar abundances are the proportions of different atoms in different types of star, and provide information about their ages and development. In the Sun, every million hydrogen atoms are accompanied by 63 000 atoms of helium, the next most abundant type.