| expansion | 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. Source: Websters Dictionary (01 Mar 1998) |
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| expansion arch | An orthodontic appliance that moves the dental structures distally, bucally, or labially, creating increased molar to molar width and arch length. (05 Mar 2000) |
| extensor digital expansion | A triangular tendinous aponeurosis including the tendon of the extensor digitorum centrally, interosseus tendons on each side, and a lumbrical tendon laterally. It covers the dorsal aspect of the metacarpophalangeal joint and the proximal phalanx. Synonym: dorsal hood, extensor aponeurosis, extensor expansion. (05 Mar 2000) |
| extensor expansion | A triangular tendinous aponeurosis including the tendon of the extensor digitorum centrally, interosseus tendons on each side, and a lumbrical tendon laterally. It covers the dorsal aspect of the metacarpophalangeal joint and the proximal phalanx. Synonym: dorsal hood, extensor aponeurosis, extensor expansion. (05 Mar 2000) |