Definify.com
Webster 1913 Edition
Treatise
1.
A written composition on a particular subject, in which its principles are discussed or explained; a tract.
Chaucer.
He published a
treatise
in which he maintained that a marriage between a member of the Church of England and a dissenter was a nullity. Macaulay.
☞ A treatise implies more form and method than an essay, but may fall short of the fullness and completeness of a systematic exposition.
2.
Story; discourse.
[R.]
Shak.
Webster 1828 Edition
Treatise
TRE'ATISE
,Noun.