Ellipticity

Ellipticity is a fancy word that describes the shape of something. Imagine you have a ball. If the ball is round like a circle, it has no ellipticity. But if you squeeze the ball from both sides, it becomes flattened and takes on an elliptical shape.

Scientists measure ellipticity by comparing the length of the ball in the short direction to the length of the ball in the long direction. If the ball is round, the short and long directions are the same length and the ellipticity is zero. But if the ball is flattened, the short direction is much smaller than the long direction, and the ellipticity is greater than zero.

Ellipticity can be used to describe lots of things in science, like galaxy shapes or the way light bounces off surfaces. Basically, it's just a way to talk about how things look when they're not perfectly round.