Gamma is the third letter of the Greek alphabet, written as Γ (uppercase) or γ (lowercase). The Greek alphabet starts with alpha, beta, gamma, much like our alphabet starts with A, B, C. Scientists and mathematicians use Greek letters all the time when they run out of regular letters or need special symbols.

You'll see gamma used in many different fields. In science, gamma rays are a powerful type of radiation that comes from space and radioactive materials. They're more energetic than X-rays and can pass through many materials, which is why scientists study them carefully. Astronomers detect gamma rays from distant exploding stars and black holes.

In photography and video games, gamma describes how bright an image appears on a screen. Adjusting the gamma settings can make dark scenes easier to see without washing out the bright parts.

Scientists also use gamma to label things when they've already used alpha and beta. For instance, when naming different versions of a virus or ranking the brightness of stars in a constellation, they'll work through the Greek alphabet: the brightest star is alpha, second-brightest is beta, third is gamma, and so on.