### Theory:

A parallelogram is a quadrilateral whose opposite sides are parallel and equal.

Here $$ABCD$$ is a parallelogram.

The side $$AB$$ is parallel to the side $$CD$$ and the side $$AD$$ is parallel to the side $$BC$$.

Also, the length $$AB = CD$$ and $$AD = BC$$.
Example:
Consider the parallelogram $$PQRS$$ with its sides measures $$6 cm$$ and $$8 cm$$.

In here the side $$PQ$$ is parallel to $$RS$$ and the side $$PS$$ is parallel to $$QR$$.

Also, it is clear that the length $$PQ = RS = 6 cm$$ and the length $$PS = QR = 8 cm$$.
Elements of parallelogram:

Parallelogram is made up of four sides and four angles. There are some terms we usually use to denote parallelogram.

They are:
1. Opposite sides
2. Opposite angles
Let's see the elements of the parallelogram $$ABCD$$.
1. The side $$AB$$ is opposite to the side $$CD$$ and the side $$AD$$ is opposite to the side $$BC$$.
2. The angle $$A$$ is opposite to the angle $$C$$ and the angle $$B$$ is opposite to the angle $$D$$.
3. The side $$AB$$ is adjacent to the side $$BC$$ because one of the sides starts where the other ends. In here, the side $$AB$$ ends at the vertex $$B$$ and the side $$BC$$ starts from there.
4. The angles $$A$$ and $$B$$ are adjacent angles as they are at the ends of the same side $$AB$$.