logic, arrangement, reason, justice, truth

彼の説明は理由が明確で、とても理解しやすかった。

His explanation had clear reasons and was very easy to understand.

物理の授業で、重力の理論を学んだ。

In physics class, we learned the theory of gravity.

この問題の解答は複雑だが、理屈は簡単だ。

The solution to this problem is complicated, but the logic is simple.