A perimeter's a path that surrounds an area. The word comes from the Greek peri (around) and meter (measure). The term may be used either for the path or its length. The perimeter of a circular area's called circumference. Practical uses Calculating the perimeter has considerable practical applications. The perimeter can be used to calculate the length of fence required to surround a yard or garden. The perimeter of a wheel (its circumference) describes how far it'll roll in one revolution. S… (More on Perimeter)