The natural sciences as a field (including physics, chemistry, biology, etc.).
理科は物理・化学・生物などの分野を含む。
Science includes fields such as physics, chemistry, and biology.
その研究は理科の分野に属する。
That research belongs to the sciences.
理科の実験では安全に注意する必要がある。
You need to pay attention to safety during science experiments.
A science department or science course at a university (i.e., STEM area).
その大学には複数の理科の学科が設置されている。
That university has several science departments.
彼は理科系のコースを選んで工学を学んだ。
He chose a science course and studied engineering.
Science as a school subject (elementary/junior high), involving experiments and observation to learn about nature.
小学校では理科の授業で植物の観察をした。
In elementary school science class we observed plants.
理科のテストで苦手な単元が出た。
A topic I'm weak at appeared on the science test.