In obsolete|lang=en terms the difference between tract and duct is that tract is (obsolete) to draw out; to protract while duct is (obsolete) guidance; direction. As nouns the difference between tract and duct is that tract is an area or expanse while duct is a pipe, tube or canal which carries gas or liquid from one place to another. As verbs the difference between tract and duct is that tract is (obsolete) to pursue, follow; to track while duct is to channel something through a duct (or series of ducts). In obsolete|lang=en terms the difference between tract and duct is that tract is (obsolete) to draw out; to protract while duct is (obsolete) guidance; direction.