If it is a more recent edition of a play (as most Shakespeare plays are, for example), you need to include the bibliographical details for that edition.
You will need:
Author’s Surname, Initials. (Year of edition) Title of the play. Edited by Editor’s Surname, Initials. Place of publication: Publisher.
Shakespeare, W. (1984) Othello. Edited by Sanders, N. Cambridge: University of Cambridge Press.
In-text citation: (Shakespeare, 1984)