# cross section

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Related to cross section: Scattering cross section

## cross section

**1.**

*Maths*a plane surface formed by cutting across a solid, esp perpendicular to its longest axis

**2.**a section cut off in this way

**3.**

*Physics*a measure of the probability that a collision process will result in a particular reaction. It is expressed by the effective area that one participant presents as a target for the other

## Cross Section

in hydraulics, the cross section of a liquid stream (in a pipeline, channel, or river) perpendicular to the direction of the flow velocity. If the liquid motion is continuously changing, the cross section is taken as flat and equal to the cross section area of the flow.

## cross section

[′krȯs ‚sek·shən] (geology)

A diagram or drawing that shows the downward projection of surficial geology along a vertical plane, for example, a portion of a stream bed drawn at right angles to the mean direction of the flow of the stream.

An actual exposure or cut which reveals geological features.

(graphic arts)

A diagram or drawing representing a cut at right angles to an axis.

(mapping)

A horizontal grid system that is laid out on the ground for determining contours, quantities of earthwork, and so on, by means of elevations of the grid points.

(mathematics)

The intersection of an

*n*-dimensional geometric figure in some euclidean space with a lower dimensional hyperplane.A right inverse for the projection of a fiber bundle.

(physics)

An area characteristic of a collision reaction between atomic or nuclear particles or systems, such that the number of reactions which occur equals the product of the number of target particles or systems and the number of incident particles or systems which would pass through this area if their velocities were perpendicular to it. Also known as collision cross section.

## cross section

A representation of a building, or portion thereof, drawn as if it were cut vertically to show its interior; often taken at right angles to the longitudinal axis of the building.