The crossword solution for the term 'THEY MAY BE DIMINISHING' is 'RETURNS'. This term is often used to refer to the profits or income that a business or individual receives from an investment or activity. It can also refer to the amount of money that is paid back to a customer after a purchase or service. In both cases, the RETURNS may be diminishing over time due to various factors such as inflation, competition, or changes in the market.