This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
Breach of contract may be made in either of two ways. (1) One party to the contract may by word or act indicate that the contract is no longer binding upon him, and the adversary party may elect to treat this as breach. The chief classes of breach of this sort are as follows: (a) One party to the contract may renounce the obligation of the contract and treat it as no longer binding upon him. In certain classes of cases this will give the adversary party the right to treat such conduct as breach where it occurs before performance is due.1 In all classes of contracts such renunciation when performance is due gives the adversary party the right at his election to treat the contract as discharged,2 and in certain classes of cases he is required to accept it as a discharge, leaving him his right of action for damages, (b) One party to a contract may make performance impossible, either on his own part or on the part of the adversary party. This may occur either before performance is due or when performance is due.3 (2) The other way in which breach may occur is where one party, without in any way repudiating his obligation under the contract, either does not perform or tenders defective performance which is not even substantial performance.