Expansion

the act or process of expanding.
the state or quality of being expanded.
the amount or degree of expanding.
an expanded, dilated, or enlarged portion or form of a thing:
The present article is an expansion of one he wrote last year.
anything spread out; expanse.
Mathematics.

the development at length of an expression indicated in a contracted form, as a 2 + 2 ab + b 2 for the expression (a + b) 2 .
any mathematical series that converges to a function for specified values in the domain of the function, as 1 + x + x 2 + … for 1/(1 − x) when x < 1. Machinery. that part of the operation of an engine in which the volume of the working medium increases and its pressure decreases. an increase in economic and industrial activity (opposed to ). additional content for a video game, card game, board game, etc., that significantly expands or alters the way the game is played: I really improved my deck with cards from the latest expansion. You can play the stand-alone expansion without ever buying the original game. Contemporary Examples

This would be an expansion of the way we usually handle insurance requirements.
Should People Be Forced to Buy Liability Insurance for their Guns? Megan McArdle December 27, 2012

Currently, Taylor is planning an expansion of his works to other parts of the globe.
Artist Jason deCaires Taylor’s Underwater Sculptures Are a Sight to Sea Justin Jones April 6, 2014

Mexico at the time was in expansion, full of possibility and hope.
My Father Sergio Muñoz Bata’s Friendship With Novelist Carlos Fuentes Lorenza Muñoz May 15, 2012

The Royal Navy, Zambellas said, “is seeing signs of expansion—which is a really weird place to be.”
Britain’s High-Tech New Plan to Rule the Waves Bill Sweetman August 13, 2014

Nor will it slow the ongoing skirmish over the expansion of U.S. coal-export facilities in the Pacific Northwest.
A Desperate Need for Electricity in China and Other Developing Countries Is Fueling Global Coal Use Robert Bryce December 17, 2012

Historical Examples

This vapor is rendered intensely cold by expansion, and this cold is imparted to the water in tank a to freeze it.
The Progress of Invention in the Nineteenth Century. Edward W. Byrn

I will not run the risk of weakening this reasoning by expansion.
Old-Fashioned Ethics and Common-Sense Metaphysics William Thomas Thornton

The degree of displacement of the fragments depends upon the extent to which the expansion of the quadriceps tendon is lacerated.
Manual of Surgery Volume Second: Extremities–Head–Neck. Sixth Edition. Alexander Miles

Such was the law of expansion; the earth was the heritage of the most numerous race.
Fruitfulness Emile Zola

“I give you my word of honour,” said Julien, with all an honest man’s expansion of heart.
The Red and the Black Stendhal

noun
the act of expanding or the state of being expanded
something expanded; an expanded surface or part
the degree, extent, or amount by which something expands
an increase, enlargement, or development, esp in the activities of a company
(maths)

the form of an expression or function when it is written as the sum or product of its terms
the act or process of determining this expanded form

the part of an engine cycle in which the working fluid does useful work by increasing in volume
the increase in the dimensions of a body or substance when subjected to an increase in temperature, internal pressure, etc
n.

1610s, “anything spread out;” 1640s, “act of expanding,” from French expansion, from Late Latin expansionem (nominative expansio) “a spreading out,” noun of action from past participle stem of Latin expandere (see expand).

expansion ex·pan·sion (ĭk-spān’shən)
n.

An increase in size.

The spreading out of a structure, such as a tendon.

expansion
(ĭk-spān’shən)

An increase in the volume of a substance while its mass remains the same. Expansion is usually due to heating. When substances are heated, the molecular bonds between their particles are weakened, and the particles move faster, causing the substance to expand.

A number or other mathematical expression written in an extended form. For example, a2 + 2ab + b2 is the expansion of (a + b)2.