The Collaborative International Dictionary of English v.0.48:

Retinol \Ret"i*nol\, n. [Gr. ??? resin + L. oleum oil.]
   1. (Chem.) A hydrocarbon oil C32H16, obtained by the
      distillation of resin, -- used as a solvent, as an
      antiseptic, and in printer's ink.
      [1913 Webster +PJC]

   2. One of the compounds which function as vitamin A. Called
      also vitamin A, vitamin A1 and vitamin A alcohol.
      See vitamin A1.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

vitamin A2 \vitamin A2\ n.
   dehydroretinol (C20H28O), one of the substances also called
   vitamin A. It has about 40% of the bioactivity of vitamin
   A1.

   Syn: dehydroretinol.
        [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

vitamin A \vitamin A\ n.
   any of several related fat-soluble vitamins (such as retinol)
   essential for normal vision; it also prevents night blindness
   or inflammation or dryness of the eyes.

   Syn: antiophthalmic factor, axerophthol.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

vitamin A1 \vitamin A1\ n.
   retinol (C20H30O), one of the substances also called
   vitamin A. It is also called more specifically vitamin A
   alcohol. It is a required factor for human nutrition. The
   USP unit of activity is equal to 0.30 micrograms of retinol.

   Syn: retinol.
        [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

axerophthol \axerophthol\ n.
   1. a vitamin essential for normal vision (C20H30O); it
      prevents night blindness or inflammation or dryness of the
      eyes; same as vitamin A. One U.S.P. unit of vitamin A is
      equivalent to 0.30 micrograms of pure vitamin A alcohol.

   Syn: vitamin A; vitamin A alcohol; antiophthalmic factor;
        biosterol; retinol; A.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

vitamin A
    n 1: any of several fat-soluble vitamins essential for normal
         vision; prevents night blindness or inflammation or dryness
         of the eyes [syn: vitamin A, antiophthalmic factor,
         axerophthol, A]