The Collaborative International Dictionary of English v.0.48:
Formula \For"mu*la\, n.; pl. E. Formulas, L. Formul[ae].
[L., dim. of forma form, model. SeeForm, n.]
1. A prescribed or set form; an established rule; a fixed or
conventional method in which anything is to be done,
arranged, or said.
2. (Eccl.) A written confession of faith; a formal statement
3. (Math.) A rule or principle expressed in algebraic
language; as, the binominal formula.
4. (Med.) A prescription or recipe for the preparation of a
5. (Chem.) A symbolic expression (by means of letters,
figures, etc.) of the constituents or constitution of a
Note: Chemical formul[ae] 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
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.