Meaning of PRO in English

I. ˈprō noun

( plural pros )

Etymology: Middle English, from Latin, preposition, for — more at for

Date: 15th century

1. : an argument or evidence in affirmation

an appraisal of the pro s and cons

2. : the affirmative side or one holding it

II. adverb

Etymology: pro-

Date: 15th century

: on the affirmative side : in affirmation

much has been written pro and con

III. preposition

Etymology: Latin

Date: 1817

: in favor of : for

IV. noun or adjective

Date: 1866

: professional

Merriam-Webster's Collegiate English vocabulary.      Энциклопедический словарь английского языка Merriam Webster.