A series of four related works, such as books, plays, or operas. The author announced that the final book in her tetralogy would be released next year.
A group of four related items or elements. The museum's exhibit featured a tetralogy of paintings that depicted the changing seasons.
A set of four related symptoms, defects, or abnormalities occurring together, especially as a congenital medical condition. Tetralogy of Fallot is a tetralogy characterized by four specific heart defects present at birth.