Describes something based on theory rather than practice or experience. Often used in academic or analytical contexts.
His explanation is theoretical and hard to understand.
It's theoretically possible, but difficult in practice.
理論的 (based on theory, as opposed to practice) is easy to confuse with 論理的 (following sound logical reasoning) because the kanji are simply reversed.
Compound of 理論 (theory) + 的 (-like, -ical).