Easing: Readonly<{
    Back: Readonly<EasingFunctionGroup>;
    Bounce: Readonly<EasingFunctionGroup>;
    Circular: Readonly<EasingFunctionGroup>;
    Cubic: Readonly<EasingFunctionGroup>;
    Elastic: Readonly<EasingFunctionGroup>;
    Exponential: Readonly<EasingFunctionGroup>;
    Linear: Readonly<EasingFunctionGroup & {
        None: EasingFunction;
    }>;
    Quadratic: Readonly<EasingFunctionGroup>;
    Quartic: Readonly<EasingFunctionGroup>;
    Quintic: Readonly<EasingFunctionGroup>;
    Sinusoidal: Readonly<EasingFunctionGroup>;
    generatePow(power?: number): EasingFunctionGroup;
}> = ...

The Ease class provides a collection of easing functions for use with tween.js.