What is the meaning of expansion?

noun

• The act of increasing (something) in size or volume or quantity or scope.
  • synonyms: enlargement
• A function expressed as a sum or product of terms.
  • usage: "the expansion of (a+b)^2 is a^2 + 2ab + b^2"
• A discussion that provides additional information.
  • synonyms: enlargement, elaboration
• Adding information or detail.
  • synonyms: expanding upon