noun
Geometric term for the measure of how much a conic section deviates from being circular.
楕円の離心率は0から1の間の値をとる。
The eccentricity of an ellipse takes a value between 0 and 1.
離心率が0のとき、その円錐曲線は
When the eccentricity is 0, the conic section is a circle.