(מ"י) על, ב-, ל-

prep. on, atop

předlož. na; po; o

Przyim. na; po; przy

(prep.)
On; -- used in all the senses of that word, with which it is interchangeable.
  

verb
(a) to do something as the result of something which has been said; he acted upon your suggestion
(b) to have an effect on; the antibiotic acted quickly on the infection