\For"mu*la\, n.; pl. E. {Formulas}, L. {Formul[ae]}.
[L., dim. of forma form, model. See{Form}, 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
   of foctrines.

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
   medicinal compound.

5. (Chem.) A symbolic expression (by means of letters,
   figures, etc.) of the constituents or constitution of a
   compound.

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
      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.