Source : Webster's Revised Unabridged Dictionary (1913)

Saccharin \Sac"cha*rin\ (s[a^]k"k[.a]*r[i^]n), n. [F., from L.
   saccharon sugar.] (Chem.)
   A bitter white crystalline substance obtained from the
   saccharinates and regarded as the lactone of saccharinic
   acid; -- so called because formerly supposed to be isomeric
   with cane sugar (saccharose).

Source : WordNet®

saccharin
     n : a crystalline substance 500 times sweeter than sugar; used
         as a calorie-free sweetener