What is what does eccentricity means?

Eccentricity is a measure of how much an object's shape deviates from a perfect circle. It is a mathematical parameter that describes the shape of an ellipse, which is a geometric shape that looks like a stretched-out circle. The eccentricity of an ellipse ranges from 0 to 1, with a value of 0 representing a perfect circle, and a value of 1 representing a line segment. The higher the eccentricity, the more flattened the ellipse becomes. Eccentricity is commonly used in astronomy to describe the shape of planetary orbits around a star, with more eccentric orbits having a higher degree of variation in distance from the star over the course of a year.