The perimeter is the total distance around the outside of a two-dimensional shape. To find the perimeter, you add up the lengths of all the sides. For example, in a rectangle, you would add the lengths of the two longer sides and the two shorter sides together. Different shapes have different formulas for calculating their perimeter. For instance, the perimeter of a square is found by multiplying the length of one side by four, while the perimeter of a triangle is the sum of the lengths of all three sides. Understanding perimeter is useful in various fields, including architecture and landscaping.