alpha; A, α +

(Greek: ; beginning, first of anything; first letter of the Greek alphabet; used in physics and chemistry to designate a variety of series or values)

1. The first letter of the Greek alphabet represented in the English alphabet as "a".
2. Relating to or being in alphabetical order.
3. Designating the first in order of importance or discovery; such as, the alpha test.
4. In computer science, the first test version; a description of the first working version of a new hardware or software product or upgrade.

Some features of the product may not be implemented in the alpha version and the discovery of significant bugs is usually anticipated.

5. A description of an the atom nearest to a particular atom or group of atoms in an organic molecule.
6. Indicating the first of a series of radiations or emissions arranged in order of increasing frequency; for example, alpha rays, alpha particle.
alpha adrenergic blockers; adrenoceptor-blocking agents; alpha blockers
These drugs stop the stimulation of alpha-adrenergic receptors at the nerve endings of the sympathetic nervous system by hormones with adrenaline-like characteristics.
alpha and omega
1. The first and last; signifies God's eternity.
2. The basic meaning of something; the crucial part; the most important aspect of something.

The beginning and the end, the first and the last, as in "She had to master the alpha and omega of the new computer program before she could even begin."

This idiom and its meaning, based on the first and last letters of the Greek alphabet, appears in the New Testament (Revelation 1:8): "I am Alpha and Omega, the beginning and the ending, saith the Lord," where it is repeated three more times.

alpha arc
A reference to the sequence of a stimulus leading to motor behavior via a simple sensorimotor path.

Beta arc refers to arousal of higher cortical paths by the functioning of an alpha arc; thus, leading to a "sensation" rather than simple "awareness", and not by an outside stimulus directly.

The term alpha arc is approximately equivalent to immediate response in Watson's behavioristic psychology, while the term beta arc is roughly equivalent to Watson's delayed response or implicit behavior.

Alpha Centauri
In astronomy, the principal star in the constellation of Centaurus; the third brightest star in the heavens.
alpha decay
In alpha decay, an alpha particle (two protons and two neutrons) is emitted from a nucleus and the atomic number decreases by two to form a new nucleus.

An example would be when an atom of uranium isotope of mass 238, on emitting an alpha particle, becomes an atom of thorium, mass 234.

alpha error, false positive
The statistical error made in testing a hypothesis when it is concluded that a result is positive, but it really is not.
alpha helix
A spiral arrangement of amino acids in certain protein molecules, forming a cylinder with side groups projecting outward.
alpha iron
The common allotrope of iron, stable below 770 degrees and having a cubic crystalline structure and magnetic properties.
alpha particle
The positively charged, high-energy, particles emitted from the nucleus of a radioactive atom.

They consist of two neutrons and two protons and so they are identical to the nucleus of a helium atom and are one of the products of the spontaneous disintegration of radioactive elements; such as, radium and thorium.

The process of emission, alpha decay, transforms one element into another, decreasing the atomic (or proton) number by two and the atomic mass (or nucleon number) by four.

It is a product of disintegration of various isotopes of both natural and artificial radioactive elements.

alpha particles, alpha rays
Radioactive, positively charged particles, two protons and two neutrons, ejected at high speeds in certain atomic disintegrations.
alpha privative
In Greek grammar, a prefix having negaitive or privative force, as in atheos, "godless".

A-, an-, as prefixed to terms or stems of Greek or Latin origin, often means "apart from" or "not concerned with"; for example, an amoral approach to economics is one that is "not concerned with moral issues".

alpha rhythm, alpha wave
1. A pattern of slow brain waves (alpha waves) in normal people at rest with closed eyes, thought by some to be associated with an alert but daydreaming mind.
2. The normal brainwave in the electroencephalogram of a person who is awake but relaxed.
3. A pattern of smooth, regular electrical oscillations in the human brain that occur when a person is awake and relaxed.

As recorded by the electroencephalograph, alpha waves have a frequency of 8 to 13 hertz.

alpha star
A star-like formation in a photographic emulsion, consisting of short heavy tracks identifying the paths of slow alpha particles emitted from a radioactive element.
alpha wave training
A type of biofeedback when alpha brain waves (7.5-13.5 cps) are characteristic of relaxed and peaceful wakefulness or the alpha state.

In alpha biofeedback training, the subject receives information on his or her EEG as a means of achieving a state of relaxation.

In one technique, a tone sounds in the absence of alpha waves and disappears when the subject produces alpha waves.

You can see all of the letters of the Greek Alphabet on this page.