Find an equation of an ellipse with vertices (0, -4) and (0, 4) and e = 1 / 4.
The eccentricity of an ellipse is defined as e = c / a. For an ellipse, 0 < c < a, so 0 < e < 1, when e is close to 0, an ellipse appears to be nearly circular. When e is close to 1, an ellipse is very flat.