- Understand that contracts are classified according to the criteria of explicitness, mutuality, enforceability, and degree of completion and that some noncontract promises are nevertheless enforceable under the doctrine of promissory estoppel.
- Keep your eyes (and ears) alert to the use of suffixes (word endings) in legal terminology that express relationships between parties.
Some contracts are written, some oral; some are explicit, some not. Because contracts can be formed, expressed, and enforced in a variety of ways, a taxonomy of contracts has developed that is useful in grouping together like legal consequences. In general, contracts are classified along four different dimensions: explicitness, mutuality, enforceability, and degree of completion. Explicitness is the degree to which the agreement is manifest to those not party to it. Mutuality takes into account whether promises are given by two parties or only one. Enforceability is the degree to which a given contract is binding. Completion considers whether the contract is yet to be performed or whether the obligations have been fully discharged by one or both parties. We will examine each of these concepts in turn.