Bayer designation

star naming system in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name

The Bayer designation for stars uses Greek letters to assign names to stars. For example:

It usually starts with the letter alpha (α) assigned to the brightest star in the constellation, then going down the Greek alphabet to assign letters for other stars (beta, gamma, delta, etc.) in order of decreasing brightness.