Numerical prefixes are words that are added to the beginning of a number to indicate its magnitude. PENTA (5 letters) is a numerical prefix meaning five, DECI (4 letters) means one tenth, TRI (3 letters) means three, NONA (4 letters) means nine, OCTO (4 letters) means eight, DECA (4 letters) means ten, TETRA (5 letters) means four, SEMI (4 letters) means half, HEPTA (5 letters) means seven, DODEC (5 letters) means twelve, HEXA (4 letters) means six, OCTA (4 letters) means eight, UNI (3 letters) means one, OCT (3 letters) means eight, HEPT (4 letters) means seven, SEXI (4 letters) means six, TETR (4 letters) means four, XXXX (4 letters) means four, SAYSO (5 letters) means six, QUADRI (6 letters) means four, and AREACODE (8 letters) means an area code.