na-adjective
conceptual; ideational; notional
Refers to something existing as an idea or concept rather than as a concrete reality. Often used in philosophical or abstract discussions.
彼の説明は観念的で、具体的な例がなかった。
His explanation was conceptual and lacked concrete examples.
na-adjective
Describes something that is based on theory or abstract reasoning rather than practical application. Can carry a slightly negative nuance of being impractical or detached from reality.
その理論は観念的すぎて、現実の問題に使えない。
That theory is too theoretical to be applied to real-world problems.
抽象的 means 'abstract' and focuses on the lack of concrete form, whereas 観念的 emphasizes the mental or ideal aspect.
Derived from 観念 (idea, notion) + the adjectival suffix 的 (-like, -tic). 観念 itself is a Sino-Japanese word composed of 観 (view, outlook) and 念 (thought, sense).