The time taken by a planet to complete one revolution is called the period of revolution. Let's understand this concept in detail.

Period of Revolution:
The period of revolution refers to the time taken by a planet to complete one orbit around its star. In the context of our solar system, it is the time taken by a planet to complete one orbit around the Sun. Each planet in our solar system has its own unique period of revolution.

Understanding Planetary Motion:
Planets revolve around the Sun in elliptical orbits. The Sun is located at one of the foci of the elliptical orbit. As a planet travels along its orbit, it experiences gravitational force from the Sun, which keeps it in its path.

Comparison with Period of Rotation:
It is important to note that the period of revolution is different from the period of rotation. The period of rotation refers to the time taken by a planet to complete one full rotation on its axis. This is what determines the length of a planet's day. For example, Earth takes approximately 24 hours (1 day) to complete one rotation on its axis.

Calculation of Period of Revolution:
The period of revolution of a planet can vary depending on its distance from the Sun. Planets that are closer to the Sun experience a stronger gravitational force, which causes them to orbit at a faster speed. Consequently, planets closer to the Sun have shorter periods of revolution compared to those farther away.

Examples:
- Mercury, being the closest planet to the Sun, has a period of revolution of approximately 88 Earth days.
- Venus takes around 225 Earth days to complete one revolution.
- Earth takes about 365.25 days (1 year) to orbit the Sun.
- Mars has a period of revolution of approximately 687 Earth days.

Conclusion:
In conclusion, the period of revolution is the time taken by a planet to complete one orbit around its star, such as the Sun. It is an important concept in astronomy and helps us understand the motion and characteristics of planets in our solar system.