The crossword solution for the term 'Roman Number' is TRE, which is a THREE letter word. TRE is an abbreviation of the Latin word 'TRES', which means 'THREE'. This is a reference to the Roman numeral system, which uses letters to represent numbers. The letter T stands for the number 10, R stands for the number 100, and E stands for the number 1. Therefore, TRE is a representation of the number 111 in the Roman numeral system.