acuity
Sharpness of the senses or mind.
Acuity refers to sharpness or keenness, especially of the senses or mind. Someone with high visual acuity can see tiny details clearly from far away: they might spot a hawk circling high overhead when everyone else sees just a speck. A person with excellent mental acuity thinks quickly and grasps complex ideas easily.
The word comes from Latin acuere, meaning “to sharpen.” Think of acuity as the opposite of dullness: it's that quality of being finely tuned and precisely focused, whether you're looking at something, listening to something, or thinking about something.