歯科
しか · shika · JLPT N1 · noun
dentistry
🦷 歯 (tooth) + 科 (department or field of study) = the tooth department, i.e. dentistry
科 marks a branch of study or medical specialty, as in 内科 (internal medicine). Adding it to 歯 (tooth) names the specialty that deals with teeth.
科 — grain 禾 + measure 斗
科 combines 禾 (grain) and 斗 (a dipper/measure), originally depicting the act of measuring or grading grain. From this, it extended to mean classification, category, and branch of study. Today it commonly appears in words for science (科学) and academic disciplines.