# chord

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## chord

(kôrd), in geometry, straight line segment both end points of which lie on the circumference of a circle or other curve; it is a segment of a secantsecant,
in mathematics. 1 In geometry, a secant is a straight line cutting a curve or surface. If it intersects the curve in two different points, as in the secant of a circle, the segment of the secant between the points is called a chord.
. A chord passing through the center of a circle is a diameter. In the same circle or in equal circles, equal chords subtend equal arcs and equal central angles.

## chord,

in music, two or more simultaneously sounding pitches. In tonal music the fundamental chord is called the triad. It consists of three pitches, two a perfect fifth apart and a third pitch a major or minor third lower, forming respectively the major or minor triad. However, a triad may instead be diminished or augmented, or may contain dissonant elements such as a seventh. In atonal music, other types of chord formations occur. It is, however, an essential property of a chord that it be conceived as an entity, that its constituent notes "fuse" rather than merely coincide in time.

## Chord

A principal member or pair of members of a truss extending from one end to the other, to resist bending.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Chord

the simultaneous combination of several notes of different pitch, auditorily perceived as a unity of sound.

Chords are differentiated by the quantitative and interval composition of the notes which make them up. Basically, a chord’s notes are arranged by thirds, proceeding upward from the lowest tone. Each one has its own name (according to the interval between it and the lowest note): the basic tone or root, the third, fifth, seventh, and so on. The fundamental kinds of chords are the triad (consisting of three different notes), the seventh (consisting of four), the ninth (five), and the eleventh (six). Triads are of four types: major (a major and a minor third), minor (a minor and a major third), diminished (two minor thirds), and augmented (two major thirds). Seventh chords are formed from triads (other than augmented triads) with the addition of a minor or major third above the chord. Sevenths may be major, minor, or diminished, depending upon the interval of the seventh between the extreme notes.

Shifting the notes of a chord—that is, moving the basic tone to one of the higher voices—is called inversion. In such cases the designation of the chord changes. A triad has two inversions (chord of the sixth and six-four chord). A seventh chord has three inversions (five-six chord, three-four chord, and chord of the second). The ninth and eleventh chords are primarily used in their root forms; their inversions have no independent designations. Chords which are built on fourths occur occasionally.

V. A. VAKHROMEEV

## Chord

a line segment connecting two points of a curve or surface.

## chord

[kȯrd]
(acoustics)
A combination of two or more tones.
(aerospace engineering)
A straight line intersecting or touching an airfoil profile at two points.
Specifically, that part of such a line between two points of intersection.
(architecture)
The span of an arch.
(civil engineering)
The top or bottom, generally horizontal member of a truss.
(mathematics)
A line segment which intersects a curve or surface only at the endpoints of the segment.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## chord

chord, 3
chord, 1
1. A principal member of a truss which extends from one end to the other, primarily to resist bending; usually one of a pair of such members.
2. The straight line between two points on a curve.
3. The span of an arch.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

## chord

An imaginary straight line joining the center of the leading and trailing edges of a cross section of an airfoil. The mean chord is used as a reference datum for laying out the curve of the airfoil. Also called a chord line.