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In mathematics, the eccentricity of a conic section is a non-negative real number that uniquely characterizes its shape. One can think of the eccentricity as a measure of how much a conic section deviates from being circular. In particular: The eccentricity of a circle is 0. The eccentricity of an ellipse which is not a circle is between 0 and 1.
In addition to the eccentricity (e), foci, and directrix, various geometric features and lengths are associated with a conic section. The principal axis is the line joining the foci of an ellipse or hyperbola, and its midpoint is the curve's center. A parabola has no center. The linear eccentricity (c) is the distance between the center and a ...
The eccentricity ϵ(v) of a vertex v is the greatest distance between v and any other vertex; in symbols, = (,). It can be thought of as how far a node is from the node most distant from it in the graph. The radius r of a graph is the minimum eccentricity of any vertex or, in symbols,
Horizontal eccentricity, in vision, degrees of visual angle from the center of the eye; Eccentric contraction, the lengthening of muscle fibers; Eccentric position of a surveying tripod, to be able to measure hidden points; Eccentric training, the motion of an active muscle while it is lengthening under load; Eccentricity, a deviation from ...
Angular eccentricity is not currently used in English language publications on mathematics, geodesy or map projections but it does appear in older literature. [1] Any non-dimensional parameter of the ellipse may be expressed in terms of the angular eccentricity. Such expressions are listed in the following table after the conventional definitions.
Roundness is dominated by the shape's gross features rather than the definition of its edges and corners, or the surface roughness of a manufactured object. A smooth ellipse can have low roundness, if its eccentricity is large. Regular polygons increase their roundness with increasing numbers of sides, even though they are still sharp-edged.
For example, the constant π may be defined as the ratio of the length of a circle's circumference to its diameter. The following list includes a decimal expansion and set containing each number, ordered by year of discovery. The column headings may be clicked to sort the table alphabetically, by decimal value, or by set.
The center (or Jordan center [1]) of a graph is the set of all vertices of minimum eccentricity, [2] that is, the set of all vertices u where the greatest distance d(u,v) to other vertices v is minimal. Equivalently, it is the set of vertices with eccentricity equal to the graph's radius. [3]