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Noun, pl. nodes (Medicine) 1. A hard concretion or incrustation which forms upon bones attacked with rheumatism, gout, or syphilis; sometimes also, a swelling in the neighborhood of a joint. ( 2. A pathological swelling or enlargement (as of a rheumatic joint). ( 3. A discrete mass of one kind of tissue enclosed in tissue of a different kind. ( (Astronomy) 1. The point where the orbit of a planet, as viewed from the Sun, intersects the ecliptic. The ascending and descending nodes refer respectively to the points where the planet moves from S to N and N to S. The respective symbols are ☊ and ☋. ( 2. Either of the two points where the orbit of a planet or comet intersects the ecliptic; also : either of the points at which the orbit of an earth satellite crosses the plane of the equator. ( (Physics) 1. A point, line, or surface of a vibrating body or system that is free or relatively free from vibratory motion. ( 2. A point at which a wave has an amplitude of zero. ( 3. The point of minimum displacement in a periodic system. ( (Botany) 1. A stem node. ( 2. A point on a stem at which a leaf or leaves are inserted. ( 3. A point at which a curve intersects itself in such a manner that the...

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Noun 1. (Geology), a small rock or mineral cluster. ( 2. (Medicine), a small aggregation of cells. ( 3. A rounded mass or irregular shape; a little knot or lump. ( 4. (Minerology) A small rounded lump of mineral substance (usually harder than the surrounding rock or sediment). ( 5. A small lump, swelling or collection of tissue. ( Word origin: From Latin nodulus “small knot,” diminutive of nodus...

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/näCH/ Noun, pl. notches (Anatomy) 1. V-shaped cut, indentation, or nick, especially at the edge of an object or structure. ( (Developmental biology) 1. A family of receptors, which upon binding with ligands, plays a major role in neurogenesis, specifically during lateral inhibition (wherein neuroblasts are singled-out from the neuroectoderm) and during binary cell fate specification (wherein ectodermal cells are prevented from differentiating into neuroblasts). ( (Other definitions) 1. A deep close pass; a gap. ( 2. A rounded indentation cut into the pages of a book on the edge opposite the spine. ( 3. The location in a range of mountains of a geological formation that is lower than the surrounding peaks. ( Word origin: From Middle French oche “notch,” from Old French ochier “to notch,” of unknown origin. Said to be unconnected to nock. Verb 1. Cut or make a notch into. ( 2. Notch a surface to record something....

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/ˈnōtəˌkôrd/ Noun, pl. notochords 1. A flexible rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes the nucleus pulposus of the intervertebral disc. The notochord is found ventral to the neural tube. ( 2. A flexible rodlike structure that forms the main support of the body in the lowest chordates; a primitive spine. ( 3. A similar structure found in the embryos of vertebrates from which the spine develops. ( 4. A longitudinal flexible rod of cells that in the lowest chordates (as a lancelet or a lamprey) and in the embryos of the higher vertebrates forms the supporting axis of the body. ( Word origin: coined in English by English anatomist Sir Richard Owen (1804-1892) from chord, alteration of cord (n.), by influence of Greek khorde “gut-string, string of a lyre, tripe,” + comb. form of Greek noton...

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