Gemini is one of the twelve constellations of the zodiac, appearing in the night sky as a pattern of stars representing twins. The name comes from Latin and means “the twins.” In ancient Greek mythology, these twins were Castor and Pollux, brothers known for their loyalty to each other.

If you were born between late May and late June, people say your zodiac sign is Gemini. Ancient astronomers noticed that as Earth orbits the Sun, the Sun appears to pass through different constellations during different times of year, creating what we call the zodiac. When someone mentions their zodiac sign, they're referring to which constellation the Sun appeared to be “in” when they were born.

You can spot Gemini in the winter sky in the Northern Hemisphere by looking for two bright stars sitting close together. These represent the heads of the twins. Early sailors used constellations like Gemini to navigate across oceans before modern technology existed.

The word also appears in other contexts: NASA named its second crewed spaceflight program Project Gemini because each capsule carried two astronauts, like the constellation's twins. Today, you might encounter the word as the name of various products or organizations, all borrowing the name's association with pairs or duality.