The Yogini temples of India are 9th to 12th century roofless hypaethral shrines to the yoginis, female masters of yoga in Hindu tantra, broadly equated with goddesses especially Parvati, incarnating the sacred feminine force. They remained largely unknown and unstudied by scholars until late in the 20th century. Several of the shrines have niches for 64 yoginis, so are called Chausath Yogini Temples (Chausath Yogini Mandir, from चौसठ, Hindi for 64, also written Chaunsath or Chausathi); others have 42 or 81 niches, implying different sets of goddesses, though they too are often called Chausath yogini temples. Even when there are 64 yoginis, these are not always the same.