Promissory note definition including break down of areas in the definition. Analyzing the definition of key term often provides more insight about concepts. Promissory note can be defined as: Written promise to pay a specified amount either on demand or at a definite future date; is a note receivable for lender but a note payable for the lendee. A promissory note can take many forms but it is usually has a longer time period then the standard terms related to accounts payable. Form this reason, in part, a promissory note will generally be in writing and will include interest for the time value of money.