трактат означава в английски

disquisition [disquisitions]▼(lengthy, formal discourse)
noun
[UK: ˌdɪ.skwɪ.ˈzɪʃ.n̩] [US: ˌdɪ.skwɪ.ˈzɪʃ.n̩]

tract [tracts]▼(brief treatise)
noun
[UK: trækt] [US: ˈtrækt]

treatise [treatises]▼(systematic discourse on some subject)
noun
[UK: ˈtriː.tɪs] [US: ˈtriː.təs]