How to say "theoretical" in Japanese

• 机上きじょうCommon
  no-adjectiveCovers the 'armchair, desk-bound' sense of theoretical: plans, theories, or debates worked out on paper without practical application. Typical of business or administrative talk about 机上の空論-style schemes that sound fine but fail in the real world.
• 観念的かんねんてきCommon
  na-adjectiveCovers the abstract, idea-based sense of theoretical: concepts or arguments that exist as notions rather than as concrete realities. Often carries a nuance of being vague, idealistic, or detached from practical experience.
  彼かれの福祉ふくしの概念がいねんはかなり観念的かんねんてきだ。↗

  His notion of welfare is pretty abstract.

Use 机上 for armchair, paper-only plans or discussions divorced from practice, and 観念的 for ideas that are abstract, idealized, or not grounded in reality.

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

• 理論的りろんてきtheoretical
• セオレティカルtheoretical
• 原理的げんりてきfundamental
• 仮定的かていてきhypothetical
• 仮かりhypothetical
• 机上きじょうtheoretical
• 観念的かんねんてきtheoretical
• 理論上りろんじょうtheoretical