Acuity: sharpness of thought, vision, or hearing. The ability to think accurately and clearly. Penetrating intelligence.
Acuity is insight, perception, sagacity, or astuteness.
We often use this word in the phrase “mental acuity.”
In idiomatic English, we might say that someone with mental acuity has the “mind of a steel trap.”
We tend to think that mental acuity declines with age. This explains why I feel that I have the mind of a dented, rusty steel trap.
My mind needs some WD-40.