1. The act of expanding or spreading out; the condition of being expanded; dilation; enlargement.

2. That which is expanded; expanse; extend surface; as the expansion of a sheet or of a lake; the expansion was formed of metal. "The starred expansion of the skies." (Beattie)

3. Space thought which anything is expanded; also, pure space. "Lost in expansion, void and infinite." (Blackmore)

4. Enlargement or extension of business transaction; especially, increase of the circulation of bank notes.

5. <mathematics> The developed result of an indicated operation; as, the expansion of (a + b)^2 is a^2 + 2ab + b^2.

6. The operation of steam in a cylinder after its communication with the boiler has been cut off, by which it continues to exert pressure upon the moving piston.

7. <astronomy> The enlargement of the ship mathematically from a model or drawing to the full or building size, in the process of construction.

Expansion is also used adjectively, as in expansion joint, expansion gear, etc. Expansion curve, a curve the coordinates of which show the relation between the pressure and volume of expanding gas or vapor; especially.

A cut-off valve, to shut off steam from the cylinder before the end of each stroke.

Origin: L. Expansio: cf. F. Expansion.

(01 Mar 1998)