gradient

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A rate of inclination; a slope.
• noun An ascending or descending part; an incline.
• noun Physics The rate at which a physical quantity, such as temperature or pressure, changes in response to changes in a given variable, especially distance.
• noun Mathematics A vector having coordinate components that are the partial derivatives of a function with respect to its variables.
• noun Biology A series of progressively increasing or decreasing differences in the growth rate, metabolism, or physiological activity of a cell, organ, or organism.

from The Century Dictionary.

• noun In mathematics, a rational integral homogeneous and isobaric function.
• noun In geometry, slope.
• Moving by steps; walking; gressorial: ambulatory: opposed to saltatory: said either of animals or of their gait: in heraldry, said of a tortoise used as a bearing and represented in fesse.
• In herpetology, walking or running on legs; specifically, of or pertaining to the Gradientia: correlated with salient and serpent.
• Rising or descending by regular degrees of inclination: as, the gradient line of a railroad.
• noun Same as grade, 2.
• noun In physics, the rate at which a variable quantity, as temperature or pressure, changes in value: as, thermometric gradient; barometric gradient.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Moving by steps; walking.
• adjective Rising or descending by regular degrees of inclination.
• adjective Adapted for walking, as the feet of certain birds.
• noun The rate of regular or graded ascent or descent in a road; grade.
• noun A part of a road which slopes upward or downward; a portion of a way not level; a grade.
• noun The rate of increase or decrease of a variable magnitude, or the curve which represents it.
• noun (Chem., Biochem.) The variation of the concentration of a chemical substance in solution through some linear path; also called concentration gradient; -- usually measured in concentration units per unit distance. Concentration gradients are created naturally, e.g. by the diffusion of a substance from a point of high concentration toward regions of lower concentration within a body of liquid; in laboratory techniques they may be made artificially.
• noun a post or stake indicating by its height or by marks on it the grade of a railroad, highway, or embankment, etc., at that spot.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A slope or incline.
• noun A rate of inclination or declination of a slope.
• noun calculus Of a function y = f(x) or the graph of such a function, the rate of change of y with respect to x, that is, the amount by which y changes for a certain (often unit) change in x.
• noun physics The rate at which a physical quantity increases or decreases relative to change in a given variable, especially distance.
• noun A vector operator that maps each value of a scalar field to a vector equal to the greatest rate of change of the scalar. Notation for a scalar field φ: φ

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the property possessed by a line or surface that departs from the horizontal
• noun a graded change in the magnitude of some physical quantity or dimension