A

A 1 Amplitude (2). 2 Albedo.
a-, an- Prefix meaning away from or opposite to.
abasement H. Murray's term for a need to surrender one's self or will to another, to atone for real or imagined shortcomings
abasia Inability to walk owing to impairment in motor coordination
abdominal reflex Contraction of the abdominal muscles when the overlying skin
abducens 1 The Vith cranial nerve. It innervates the external rectus muscle in the eye, which functions to rotate the eyeball inward. Also called the abducent nerve. 2 Pertaining to movement away from the central plane of the body. See abduction. 
abducent nerve abducens
abduction 1 Lateral movement of a limb away from the median plane of the body. Compare with adduction. 2 C.S. Peirce's term for the cognitive process wherebyhypotheses are generated on the basis of some known facts. Abduction, in Pierce's terms, was a fundamental component of creative thought. 
abductor - a muscle which, upon contraction, moves a limb away from the body. Compare with adductor
aberration - The act of wandering or straying from the normal course. The term enjoys wide currency and is used of the behavior of an intact organisms as well as for biological structures, physical systems, instruments, etc.
aberration, chromatic - Unequal refraction of light of different wavelengths as it passes through a lens, producing a coloured image.
aberration, mental - a nontechnical term used loosely for any mental disorder
aberration, spherical - distortions of a light wave passing through a lens produced either by the natural curvature of the lens of the irregularities in the curvature of the lens
ABI - acquired brain injury
abient - characterizing movement away from something, ant. adient.
ability - the qualities, power, competence, faculties, proficiencies, dexterities, talents, etc. that enable one to perform a specified feat in a particular time. The essence of the term is that the person can perform this task now, no further training is needed. The main distinction thus is between ability and aptitude. Ability is an individual's potential to perform; aptitude is an individual's potential for performance, or the possibility of the individual to be trained up to a specified level of ability. Intelligence tests, for example, are ability tests.
abiotic - Not compatible with life.
ablation - Removal of part of an organ. Usually refers to surgical removal. When the full organ or structure is removed, the term exterpation is generally used
Abney's Effect a perceptual phenomenon experienced when a large room is suddenly illuminated. Rather than appearing all at once, the light seems to come on first in the center of the patch and then spread to the edges. When extinguished, the edges disappear first, the center last.