Ellipses and curves
An ellipse is a curve that makes a kind of oval. Ellipses can be quite round or stretched. Whole ellipses or segments of them are often found in nature. Examples are the paths planets take orbiting the Sun and the curving edges of many plant leaves. If you draw a sloping line around a cone that is an ellipse too.
Complete ellipses and segments of them are useful shapes in product design, architecture and art.