How much in common and what are the differences between using of ENCYCLOPEDIA, PHARMACOPOEIA and DICTIONARY?

Hi Lubna,

Great question. 

Encyclopedia gives you information on a specific topic (dictionary/thesaurus would accompany this if one doesn't understand specific words)

Thesaurus gives synonyms, definition of words and also antonyms

Dictionary gives correct spelling of a word and also what it means and related words

Pharmacopoeia relates to medicines, chemicals etc  (from the Greek pharmakon meaning drug)