The answer to the crossword for the term SECOND PREFIX is NANO, which is a four-letter word. Nano is a PREFIX derived from the Greek word for 'DWARF' and is used to denote something that is extremely small. It is often used in scientific contexts to refer to objects that are measured on the nanometer scale, which is one billionth of a meter. Nano is also used in technology to refer to devices or components that are very small in size.