• 科学かがく — science
• 科目かもく — subject / curriculum item
• 教科書きょうかしょ — textbook
• 理科りか — natural sciences
• 外科げか — surgery (medical)
• 前科ぜんか — criminal record / previous offense
• 科料かりょう — monetary penalty / fine
• 百科事典ひゃっかじてん — encyclopedia

This kanji originally depicted sorting grains or items, and it now signifies categories in education, medicine, and systems. It’s widely seen in academic and institutional contexts.