the prefix a- or, before a vowel, an-, used in Greek and English to express negation or absence.
(in Greek grammar) the letter alpha (or an- before vowels) used as a negative or privative prefix. It appears in English words derived from Greek, as in atheist, anaesthetic
- Alpha radiation
a stream of alpha particles. noun alpha particles emitted from a radioactive isotope noun ionizing radiation consisting of a stream of alpha particles alpha ray n. A stream of alpha particles or a single high-speed alpha particle. alpha ray A stream of alpha particles. alpha radiation [(al-fuh)] Particles sent out by some radioactive nuclei, each […]
- Alpha ray
a stream of alpha particles. Historical Examples The alpha ray carries a positive charge of double the ionic amount. The Birth-Time of the World and Other Scientific Essays J. (John) Joly Such is a brief summary of the climax of radioactive discovery:—the birth, life and death of the alpha ray. The Birth-Time of the World […]
- Alpha receptor
a site on a cell that, upon interaction with epinephrine or norepinephrine, controls vasoconstriction, intestinal relaxation, pupil dilation, and other physiological processes.
- Alpha rhythm
a pattern of slow brain waves (alpha waves) in normal persons at rest with closed eyes, thought by some to be associated with an alert but daydreaming mind. noun (physiol) the normal bursts of electrical activity from the cerebral cortex of a drowsy or inactive person, occurring at a frequency of 8 to 12 hertz […]