The term 'letter form' is a type of document that is used to communicate information in written form. A letter form is typically composed of a heading, body, and closing. The heading includes the sender's address, date, and recipient's address. The body of the letter contains the main message, while the closing includes the sender's signature and any other pertinent information. In this crossword puzzle, the solution for the term 'letter form' is 'LEASE, ' which is a legal agreement between two parties that outlines the terms and conditions of a rental property.