In lexical semantics, opposites are words lying in an inherently incompatible binary relationship.
Graded (or gradable) antonyms are word pairs whose meanings are opposite and which lie on a continuous spectrum (hot, cold).
Relational antonyms are word pairs where opposite makes sense only in the context of the relationship between the two meanings (teacher, pupil).
For example, "undevout" is found in Webster's 1828 dictionary, while the prefix pattern of "non-person" could theoretically extend to "non-platypus."
Other examples include: mortal : immortal, exit : entrance, exhale : inhale, occupied : vacant.
A relational antonym is one of a pair of words that refer to a relationship from opposite points of view.
Other examples include: husband : wife, doctor : patient, predator : prey, teach : learn, servant : master, come : go, parent : child.