Mascara gives your eyes definition and depth.
It makes them look bigger, brighter, and more defined by adding length and volume.
One way to use mascara for definition is by applying a layer of black mascara first, followed by brown mascara on just the tips and the lower lashes.
This ticks the checkbox of ultimate definition and vibrancy, without giving the impression of over made up, stiff, cakey spider legs.
Another option is applying two coats of brown mascara instead; for a softer effect that is just as mesmerizing. But for low-key occasions.