A formal promise is a solemn and binding commitment made by one party to another. It is usually made in writing and is often legally binding. The most common terms used to describe a formal promise are 'VOW', 'OATH' and 'I shall'. A VOW is a solemn promise made to oneself or to a deity, while an OATH is a solemn promise made to a court of law or other authority. 'I shall' is a phrase used to express a strong intention to do something.