chemical formula
Refers to a representation of a chemical substance using element symbols and numbers, such as H₂O or NaCl.
The chemical formula of water is H₂O.
この化学式を見て、何の物質かわかりますか？
Looking at this chemical formula, can you tell what substance it is?
組成式 is an empirical formula showing the simplest ratio of elements, a subset of 化学式.
Compound of 化学 (かがく, 'chemistry') and 式 (しき, 'formula' or 'style').