penicillin vs. amoxicillin

any of several antibiotics of low toxicity, produced naturally by molds of the genus Penicillium and also semisynthetically, having a bactericidal action on many susceptible Gram-positive or Gram-negative cocci and bacilli, some also being effective against certain spirochetes.

a semisynthetic penicillin, C 18 H 19 N 3 O 5 S, taken orally as a broad-spectrum antibiotic.