1. Pertaining to the most desirable or favorable under existing conditions: The pilot of the passenger place waited for optimal weather conditions before taking off from the airport.
2. Relating to that which is most desirably possible under a restriction expressed or implied: William and Janice are hoping for an optimal return on their financial investment.
3. A reference to producing or likely to produce the best result: Shirley and her doctor concluded that surgery was the optimal course to take under the circumstances.

The medical report stated that eight hours of sleep is optimal for most adults.

The use of limited resources; especially, energy and time, in order to achieve certain objectives.

A control method in which a system's response to a commanded input is judged to be best as related to a specific performance criterion, considering the dynamics of the process to be controlled and the limitations of the involved measurements.