Classification of contracts

By type of formation
Express (is stated in words or oral, this contract is conscious)	Implied: · Implied-in-fact (is manifested by conduct rather than words) · Implied-in-law (is crested by operation of law in order to avoid unjust enrichment of one party)
By type of performance
Bilateral (is based on the exchange of promises)	Unilateral (involves a promise by one party and an act by the other party)	Executed (is one that is fully performed by both parties)	Executory (something remains to be done)
By enforceability
Valid (it meets all legal requirements and can be enforced by parties)	Unenforceable (does not meet all legal requirements)	Void (is made under threat or physical force)	Voidable (is made by minors, or under mental duress)