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# torus

[ **tawr**-*uh*s ]

## noun

*plural***to·ri**[tawr, -ahy].*Geometry.*- Rarely . a doughnut-shaped surface generated by the revolution of a conic section, especially a circle, about an exterior line lying in its plane.
- the solid enclosed by such a surface.

*Botany.*- the receptacle of a flower.
- a thickening of the wall membrane in the bordered pits occurring in the tracheid cells of the wood of many conifers.

*Anatomy.*a rounded ridge; a protuberant part.

torus

/ ˈtɔːrəs /

## noun

- Also calledtore a large convex moulding approximately semicircular in cross section, esp one used on the base of a classical column
- geometry a ring-shaped surface generated by rotating a circle about a coplanar line that does not intersect the circle. Area: 4π²
*Rr*; volume: 2π²*Rr*², where*r*is the radius of the circle and*R*is the distance from the line to the centre of the circle - botany another name for receptacle
- anatomy a ridge, fold, or similar linear elevation
- astronomy a dense ring of gas and dust which surrounds a dying star, containing most of the star's ejected gas

torus

/ tôr**′**əs /

, Plural *tori* tôr**′**ī

- A surface generated by rotating a circle about an axis that is in the same plane as the circle but does not intersect it. A torus resembles a donut and is a subtype of toroid.
- The torus-shaped apparatus that contains plasma in nuclear fusion reactors.

## Word History and Origins

Origin of torus^{1}

*Latin:*literally, “strand, thong, raised ridge”

## Word History and Origins

Origin of torus^{1}

## Example Sentences

A hollow torus can be cut twice — once around the tube and then along the resulting cylinder — so by this definition, it has two holes.

If the surface does not have a boundary, like a torus, the first cut must begin and end at the same point.

That there are two one-dimensional loops from which all others can be built means that the Betti number of the torus in dimension one is 2, the same as the number of Riemann’s cuts.

At each corner of the black marble bases, and touching the torus of the column, the head of a bird or animal has been carved.

The lateral arcades have similar capitals but only one torus.

At this time each pistil loosens from the torus and can be easily removed, especially if some animal touch the hooks.

The slender torus usually distinguished the eight-branch Plantagenet type, and its use here for simple diagonals is an exception.

As time went on profiles deteriorated, sharp prismatic molds succeeding to the virile torus, or molds fluid and vague.

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