molecular formula \molec"ular form"ula\, n. chem.
   an expression representing the composition of elements in a
   chemical substance, commonly consisting of a series of
   letters and numbers comprising the atomic symbols of each
   element present in a compound followed by the number of atoms
   of that element present in one molecule of the substance.
   thus the molecular formula for common alcohol ethyl alcohol
   is c2h6o, meaning that each molecule contains two carbon
   atoms, six hydrogen atoms, and one oxygen atom. the molecular
   formula may be written to provide some indication of the
   actual structure of the molecule, in which case structural
   units may be written separately. thus, ethyl alcohol can also
   be written as ch3.ch2.oh or ch3-ch2-oh, in which the
   period or dash between functional groups indicates a single
   bond between the principle atoms of each group. this formula
   shows that in ethyl alcohol, the carbon of a methyl group
   ch3- is attached to the carbon of a methylene group
   -ch2-, which is attached to the oxygen of a hydroxyl
   group -oh. a structural formula is a graphical
   depiction of the relative positions of atoms in a molecule,
   and may be very complicated.
   pjc
see also:
c2h6o ch3.ch2.oh ch3-ch2-oh ch3- -ch2- -oh 
structural formula 

alcohol \al"cohol\ a^l"k-oho^l, n. cf. f. alcool,
   formerly written alcohol, sp. alcohol alcohol, antimony,
   galena, osp. alcofol; all fr. ar. al-kohl a powder of
   antimony or galena, to paint the eyebrows with. the name was
   afterwards applied, on account of the fineness of this
   powder, to highly rectified spirits, a signification unknown
   in arabia. the sp. word has both meanings. cf. alquifou.
   1. an impalpable powder. obs.
      1913 webster

   2. the fluid essence or pure spirit obtained by distillation.
      obs. --boyle.
      1913 webster

   3. pure spirit of wine; pure or highly rectified spirit
      called also ethyl alcohol or ethanol, ch3.ch2.oh;
      the spirituous or intoxicating element of fermented or
      distilled liquors, or more loosely a liquid containing it
      in considerable quantity. it is extracted by simple
      distillation from various vegetable juices and infusions
      of a saccharine nature, which have undergone vinous
      fermentation.

   note: the ferementation is usually carried out by addition
         of brewer's yeast, saccharomyces cerevisiae to an
         aqueous solution containing carbohydrates.
         1913 webster +pjc

   note: as used in the u. s. "pharmacopoeia," alcohol
         contains 91 per cent by weight of ethyl alcohol and 9
         per cent of water; and diluted alcohol proof spirit
         contains 45.5 per cent by weight of ethyl alcohol and
         54.5 per cent of water.
         1913 webster

   4. organic chem. a class of compounds analogous to vinic
      alcohol in constitution. chemically speaking, they are
      hydroxides of certain organic radicals; as, the radical
      ethyl forms common or ethyl alcohol c2h5.oh; methyl
      forms methyl alcohol ch3.oh or wood alcohol; amyl
      forms amyl alcohol c5h11.oh or fusel oil, etc.
      1913 webster
see also:
alquifou ethyl alcohol ethanol ch3.ch2.oh saccharomyces cerevisiae c2h5.oh 
methyl alcohol ch3.oh wood alcohol amyl alcohol c5h11.oh 
fusel oil