The term 'Four Prefixes' refers to four words that all have the same prefix. The crossword solution for this term is 'TETRAS', which is a six letter word. TETRAS is a Greek prefix meaning 'four'. It is commonly used in scientific terms, such as tetrahedron (a four-sided solid figure) and tetrapod (an animal with four feet). It is also used in mathematics, such as the tetration (the fourth power of a number).