Define pie diagram? How is it constructed?

Pie diagram is a circle divided into various segments showing the per cent values of a series. This diagram does not show absolute values of each category. The values of each category are first expressed as percentage of the total value of all the categories. Such diagram is known as sector diagram. The circle comprises 360°. Accordingly, percentage of a variable are fixed as multiples of 360°. Different parts of a circle may be shaded with different colours highlighting different values.