expansion
Pluralexpansions
- 1The process of becoming larger or making something larger, or a single case of this.
Rapid expansion of the company strained its supply chain.
Scientists measured the gas's expansion as the temperature rose.
UsageUsually expansion of something, or expansion into a new place or market; say an expansion for one case of it.
Similargrowth, increase, enlargement, extension
Oppositecontraction, reduction, shrinkage, decrease
Note
It covers the physical, such as metals swelling with heat, and the social, as when Heidi Nast writes of the KKK's expansion into the Midwest.
- 2A phase of the business cycle in which economic activity, such as output and employment, keeps growing, from a low point to the next peak.
The decade-long expansion raised household incomes across the region.
Economists debate whether the current expansion can survive rising interest rates.
UsageUsed for one period of growth: an expansion, the current expansion, often set against a recession.
Oppositerecession, downturn, slump
Note
Economists tie the term to the business cycle, where an expansion is a stretch of growth and the counterpart of a recession. The Conference Board Record of 1971 contrasts a cyclical expansion with earlier expansions that began from a deeply deflated recession base. Fred Caloren, Michel Chossudovsky and Paul Gingrich (1978) note unemployment drifting upward even during expansions.
- 3Ellipsis of expansion pack.
The studio announced an expansion that doubles the size of the game's map.
Veteran players complained that the expansion broke several older quests.
- 4A newly added section or wing built onto an existing structure.
Visitors now enter through the glass expansion on the east side of the library.
The museum's new expansion, a two-story glass wing, houses its modern art collection.
Similarannex
Note
A builder's word for the structure, not the act of building it: an expansion is a place you can walk into, such as a hospital's new wing. Annex is the near-synonym. The two readings can blur, since a museum's expansion may mean the project or the new wing. A location phrase such as in the expansion points to the wing, while words of growth and timing point to the general process.
- 5In algebra, the process of writing out an expression as an equal but longer sum of terms, as when brackets are multiplied out.
The expansion of (x + 1)² gives x² + 2x + 1.
Students practiced expansion of bracketed expressions before learning to factor them.
Oppositefactorization
Note
Algebra's expansion multiplies out brackets, usually by the distributive law, so that (x + 1)² becomes x² + 2x + 1. It is the reverse of factoring and is usually taught first. The same word covers developing a function as a power series. Like spelling out an acronym, it trades a compact form for a longer one that says exactly the same thing.
Checked 7 Nov 2026 · 4 facts
- Algebraic expansion multiplies out brackets using the distributive law; (x + 1)² equals x² + 2x + 1. openstax.org
- Expansion reverses factoring. uniskills.library.curtin.edu.au
- A function's representation as a power series is called an expansion. math.fel.cvut.cz
- Multiplying out an algebraic expression preserves its value. openstax.org
Less common meanings
- 6The full form that an abbreviation or acronym stands for, or the act of writing it out in full.
House style calls for expansion of all initialisms on first mention.
Medical papers usually give the expansion of an acronym like 'MRI' the first time it appears.
UsageUsually the expansion of an acronym or short form, often given on first mention.
Note
An editor's and writer's term for spelling out a short form so that a general reader can follow. Anacronyms are the exception: these acronyms have become words in their own right, so their full form usually need not be given. The full form itself is also called the expansion.
- 7
- 8Thermal expansion as a property of a material: how much it grows as it heats, often given as the fraction of its length gained per degree.
- 9In geometry, an operation on a figure with flat faces that moves the faces apart from the center and fills the gaps with new faces.
- 10The continued action of steam in a cylinder after its supply from the boiler has been cut off, during which it goes on exerting pressure on the moving piston.
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Origin
English borrowed it from French expansion, which goes back to Latin expānsiō. Looked at from English alone, it splits into expand plus the suffix -sion.