1. The Pleiades (star cluster): This is the most common meaning. The Pleiades is an open star cluster in the constellation Taurus, easily visible to the naked eye. It's known for its beautiful blue-white stars and is often called "The Seven Sisters" due to its seven brightest stars.
2. The Pleiades (in Greek mythology): In Greek mythology, the Pleiades were seven daughters of Atlas and Pleione, who were transformed into stars after the death of their sisters, the Hyades.
3. A member of the Pleiades: In ancient Greece, the Pleiades were a group of seven poets and writers associated with the city of Thebes. This meaning is less common nowadays.
4. A group of seven: In some contexts, "pleiad" can be used as a synonym for a group of seven people or things, regardless of their specific connection to the Pleiades.
Which definition is relevant depends on the context of the word's use. For example, if you're reading a book about astronomy, "pleiad" likely refers to the star cluster. If you're reading a book about ancient Greek mythology, "pleiad" likely refers to the daughters of Atlas.