What does "formula" mean?

Additional senses

1. 2.(Math.) A rule or principle expressed in algebraic language; as, the binominal formula.
2. 3.(Med.) A prescription or recipe for the preparation of a medicinal compound.
3. 4.(Chem.) A symbolic expression (by means of letters, figures, etc.) of the constituents or constitution of a compound. Note: Chemical formulæ consist of the abbreviations of the names of the elements, with a small figure at the lower right hand, to denote the number of atoms of each element contained. Empirical formula (Chem.), an expression which gives the simple proportion of the constituents; as, the empirical formula of acetic acid is C2H4O2. -- Graphic formula, Rational formula (Chem.), an expression of the constitution, and in a limited sense of the structure, of a compound, by the grouping of its atoms or radicals; as, a rational formula of acetic acid is CH3.(C:O).OH; -- called also structural formula, constitutional formula, etc. See also the formula of Benzene nucleus, under Benzene. -- Molecular formula (Chem.), a formula indicating the supposed molecular constitution of a compound.