This is the 10854th most frequent French word.
optimal
Best or most favorable.
In this sentence, 'optimal' qualifies 'solution', indicating that the solution should be the best one achievable under the given circumstances.
Nous devons trouver une solution optimale avant la réunion.
We need to find an optimal solution before the meeting.
Here, 'optimal' is describing 'conditions' to mean that the circumstances are not ideal or favorable for the intended activity.
Les conditions météorologiques ne sont pas optimales pour un voyage en montagne.
The weather conditions are not optimal for a trip to the mountains.
Here, 'optimal' is used as an adjective to describe the best possible option that meets all conditions.