Reason, principle, or logic — the underlying rationale, rule, or explanation for how something works.
彼の説明は理にかなっている。
His explanation makes sense (is reasonable).
科学は自然の理を解き明かそうとする営みだ。
Science is an endeavor to uncover the principles of nature.
その規則には深い理がある。
There is a deep principle behind that rule.
行動する前に理を考えるべきだ。
You should consider the rationale before acting.
In Buddhist terminology, 'ri' refers to a general principle (as opposed to individual, concrete phenomena — 'ji').
禅では理と事の関係について議論されることが多い。
In Zen, the relationship between 'ri' (principle) and 'ji' (phenomena) is often discussed.
仏教の教説では、理（一般原理）と個々の事（現象）を区別して説く。
Buddhist teachings distinguish between ri (general principles) and individual phenomena (ji).
In Neo-Confucianism, 'ri' denotes the underlying principles of the cosmos — the fundamental laws or order that govern all things.
朱子学では、理は宇宙の根本原理として重視された。
In Zhu Xi's Neo-Confucianism, li (理) was emphasized as the fundamental principle of the universe.
理が万物の秩序を定めると考えられた時代がある。
There was an era when people believed that li determined the order of all things.