How to say "optimum" in Japanese

• 最適さいてきCommon
  na-adjective, no-adjectiveThe common word and the safe default: it covers 'optimum, optimal' and the broader 'most suitable, best'. Use it when choosing the best option, method, or conditions for a given purpose.
  彼かれはこの計画けいかくに最適さいてきである。↗

  He is the best for this project.
• 至適してき
  na-adjectiveA less common synonym for the 'optimal, optimum' sense; the broader 'most suitable, best' meaning belongs to 最適. Unless you have a specific reason to use it, 最適 is the word you want.

Choose 最適 for nearly all uses of 'optimum', since the common word covers 'optimal, optimum' and the broader 'most suitable, best', while 至適 is a less common synonym for the 'optimal, optimum' sense.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 最適さいてきmost suitable
• 至適してきoptimal