An Etymological Dictionary of Astronomy and Astrophysics

1. General: The act or process of expanding; the state or quality of being expanded. → expansion of the Universe.
   

2. Math.: The process of expressing a quantity, or a quantity expressed,
   as a sum of a series of terms. For example the expression (2x - 1)(x + 3) can be expanded to: 2x² + 5x - 3. See also → binomial expansion.

See also: Noun from → expand.