A tractate is a written work dealing formally and systematically with a subject; the word derives from the Latin tractatus, meaning treatise.[1]
One example of its use is in citing a section of the Talmud, when the term masekhet (מסכת) is used in conjunction with the name of the subject, for example, Masekhet Berakhoth, which is relevant to agriculture and blessings.[2]
Two further examples are the 1670 and '76 Tractatus Theologico-Politicus by Baruch Spinoza, and the 1921 Tractatus Logico-Philosophicus by Ludwig Wittgenstein.