6. Anatomy

a. any natural bulge or swelling of a structure or part, such as those that occur along the course of a lymphatic vessel (lymph node)

b. a finger joint or knuckle

(anatomy)

A knob or protuberance.

A small, rounded mass of tissue, such as a lymph node.

(astronomy)

One of two points at which the orbit of a planet, planetoid, or comet crosses the plane of the ecliptic.

One of two points at which a satellite crosses the equatorial plane of its primary.

(botany)

A site on a plant stem at which leaves and axillary buds arise.

(electronics)

A junction point within a network.

(geology)

That point along a fault at which the direction of apparent displacement changes.

(industrial engineering)

On a graphic presentation of a project, a symbol placed at the intersection of arrows that represent activities to identify the completion or start of an activity.

(neuroscience)

A point of constriction along a nerve.

(physics)

A point, line, or surface in a standing-wave system where some characteristic of the wave has essentially zero amplitude.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

in astronomy, one of the two diametrically opposite points of the celestial sphere at which the plane of the orbit of some celestial body intersects a reference coordinate plane that is either the plane of the ecliptic or of the equator. The points where the orbit intersects the reference plane are sometimes also called nodes. A distinction is made between the ascending node (astronomical symbol ), where the celestial body crosses from the southern to the northern side of the reference plane, and the descending node (symbol ), where the body crosses the reference plane in the opposite direction.

For planets, comets, and the moon the ecliptic serves as the reference plane. In this case, the position of the nodes on the celestial sphere is defined by their longitudes. When the orbits of artificial earth satellites are determined, the plane of the equator serves as the reference plane, and the positions of the nodes are given by the right ascensions of the nodes. The longitude of the ascending node and the right ascension of the ascending node are orbital elements.

For binary stars the points where the orbits intersect the plane perpendicular to the line of sight are called nodes.

in botany, the part of a shoot axis on which the leaf, the bud, and, sometimes, the adventitious roots form.

Nodes are separated by internodes. On the basis of the distance between nodes, shoots are distinguished as being long or short. Nodes form on the growing point of a shoot when the leaf rudiments first appear. At the node the procambial bundles of the developing leaf become embedded in the axis of the shoot. From these bundles and from the bundles of previously laid down leaves the common bundles of the shoot axis are formed. The common bundles constitute the entire conducting system of the axis. The anatomical structure of nodes varies, depending on the leaf arrangement, the number of procambial bundles in the leaf, and the way the bundles enter the node. Bundles of the axillary buds (branches), which form branch traces, join the conducting system of the shoot axis at the node. The structure of the shoot nodes is a taxonomic character for many plant species.

in mathematics, a type of singular, or critical, point of a differential equation (seeSINGULAR POINT). All integral curves passing through points in a sufficiently small neighborhood of a node enter the node.

In Russian mathematical literature, three different types of such nodes are distinguished: ordinary (obychnyi), degenerate (vyrozhdennyi), and special (osobyi). An ordinary node is a critical point such that all but one of the integral curves passing through the point are tangent to the same line (Figure l, a). In the case of a degenerate node, all the integral curves passing through the node are tangent to the same line (Figure l, b). In the case of a special, or dicritical (dikriticheskii), node, integral curves enter the origin from every direction (Figure l, c). In English, the first two cases are sometimes called improper nodes, and the third case is sometimes referred to as a proper node.

The term “node” is also applied to one type of singular point of a curve.

The Russian word for node—uzel—also has the meaning of knot. In topology a knot is, in the simplest case, a continuous closed space curve that does not intersect itself.