In the phonetic alphabet, Alpha represents the letter A. According to my dictionary - a very old but perfectly serviceable American Heritage circa 1969 - Alpha is also 1. the first letter in the Greek alphabet 2. the first of anything; beginning 3. the brightest or main star in a constellation 4. first in order of importance. [Greek, from a Phoenician word akin to Hebrew aleph, ALEPH.]
Here are a few Alphas you may or may not be familiar with...
Alpha Centauri - if you're a Geek like me you know this is a double star in Centaurus, the brightest in the constellation, 4.4 light years away from Earth.
Alpha Crucis - but I'll wager you didn't know this was a double star, too, in the constellation Crux, approx. 230 light years away.
Alpha Leonis - Also a star, known as Regulus, in the constellation Leo.
Alpha particle - a positively charged composite particle.
Alpha privative - the Greek negative prefix
Alpha ray - a stream of alpha particles
Apha rhythm - the most common electroencephalographic waveform found in recordings of the electrical activity of the adult cerebral cortex, characteristically 8 to 12 smooth, regular oscillations per second in subjects at rest. also called 'alpha wave.'