Centimeter : A centimeter ($cm$) is $\frac{1}{100}$ of a meter.

Length : Length is the attribute of a one-dimensional shape that can be measured with a measuring tape.

Perimeter : The perimeter of a two-dimensional shape is the length of the boundary of the shape. For a polygon this is the same as the sum of all the side lengths. For example a triangle with side lengths 1, 2 and 3cm has a perimeter of 1+2+3=6cm. The perimeter of a circle is referred to as its circumference.

Square : A square is a quadrilateral with four right angles and four equal length sides. A square is a special case of a rectangle and a special case of a rhombus.

Sum : A sum is the result of an addition.