Translation guide
Expresses that something is based on theory rather than practice, or exists only as an idea or possibility.
Describing knowledge, a field, or an approach that is abstract and not yet applied.
The most direct equivalent, used for academic or systematic theoretical frameworks.
His research is highly theoretical.
Often used adverbially to mean 'in theory' or 'theoretically speaking'.
Theoretically it's possible, but in practice it's difficult.
Referring to an idea, scenario, or possibility that is imagined rather than real.
Describing a discussion or concept that is removed from everyday reality.
理論的 is used for established theoretical frameworks (e.g., theoretical physics), while 仮説的 emphasizes that something is still a hypothesis and not yet proven.
theoretical physics
a hypothetical model
English 'theoretical' can sometimes be translated directly as 理論的, but in casual contexts, it may sound stiff. Consider rephrasing with 理屈っぽい (overly logical) or 現実的じゃない (not realistic) if the nuance is negative.
An idiom meaning 'armchair theory' or an impractical idea that only works on paper.
That plan is nothing more than a theoretical idea.
It's merely of theoretical interest.