fellow: an informal form of address for a man
entity: that which is perceived or known or inferred to have its own distinct existence (living or nonliving)
erythromycin: an antibiotic (trade name Erythrocin or E-Mycin or Ethril or Ilosone or Pediamycin) obtained from the actinomycete Streptomyces erythreus; effective against many Gram-positive bacteria and some Gram-negative