1. Circular space for the chorus and dancers in an Ancient Greek theatre.
2. In a Roman theatre, the semicircular level space between the stage and proscenium and the first semicircular row of seats.
3. In a modern theatre the space reserved for the musicians.
4. In the USA the main floor, parquet, or stalls of a theatre.
"orchaestra." A Dictionary of Architecture and Landscape Architecture. . Encyclopedia.com. (October 15, 2018). http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/orchaestra
"orchaestra." A Dictionary of Architecture and Landscape Architecture. . Retrieved October 15, 2018 from Encyclopedia.com: http://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/orchaestra