noun
physical science; natural science
Broad term for the natural sciences, especially physics, chemistry, biology, and earth sciences. Often contrasted with 文学 (humanities).
彼は理学部で物理学を専攻している。
He is majoring in physics in the Faculty of Science.
理学と工学の違いは何ですか。
What is the difference between science and engineering?
noun
Obsolete term for physics; modern Japanese uses 物理学.
See also: 物理学
明治初期には「理学」が物理学を指すこともあった。
In the early Meiji period, 理学 sometimes referred to physics.
noun
Obsolete term for philosophy; modern Japanese uses 哲学.
See also: 哲学
江戸時代の文献では「理学」が哲学の意味で使われることがある。
In Edo-period texts, 理学 is sometimes used to mean philosophy.
noun
Specifically refers to the Song-Ming school of neo-Confucianism (宋明理学). A historical philosophical term.
See also: 宋明理学
宋明理学は朱子学と陽明学を含む。
Song-Ming neo-Confucianism includes Zhu Xi's teachings and Wang Yangming's teachings.
哲学 is the standard modern word for 'philosophy'. 理学 was used historically for this meaning but is now obsolete.
From 理 (principle, reason) + 学 (study, learning). Originally a broad term for the study of principles, it was used in various historical contexts to refer to physics, philosophy, and neo-Confucianism. The modern sense is largely restricted to 'natural science' as an academic discipline.