optimum
1. [ adjective ] most desirable possible under a restriction expressed or implied
Synonyms: optimal
Examples:

"an optimum return on capital" "optimal concentration of a drug"

Related terms: best
2. [ noun ] most favorable condition or greatest degree or amount possible under given circumstances
Related terms: good optimize
Similar spelling:   optimal
  optimize
  optimist
  optimism
  optimise
  optimally
  optimistic