trea ‧ tise /ˈtriːtəs, ˈtriːtɪs, -təz/ BrE AmE noun [countable]
[ Date: 1300-1400 ; Language: Anglo-French ; Origin: tretiz , from Old French traitier ; ⇨ ↑ treat 1 ]
a serious book or article about a particular subject
treatise on
a treatise on medical ethics