From Hull AWE
Originally it was a Latin preposition, used also as a prefix (and an adjective) with a broad range of meanings, of which the main ones were 'in front of' or 'forwards'; 'outwards'; 'down'; 'before' (in time or space'); 'for' or 'on behalf of'.
- In modern English, two nouns which are colloquial shortenings of longer words should normally be avoided in academic English.
- The expression 'a[n old] pro' is a label for a professional (often a boxer; but it can be applied to followers of any activity. In the days when sport was rigidly divided into amateur and professional, it was applied to cricketers, golfers and so on who were paid to play.) Professional is derived from words meaning 'to acknowledge in front of the people or publicly'.
- Pro is often applied dismissively in everyday speech to a prostitute. (This word is derived from Latin meaning '[one] made to stand in front of (pro-) the people to expose her shame'.
- A third noun is to be seen in academic writing, though it too may be frowned on by pedants: pro meaning 'an argument for', as opposed to a con, an argument against. For a caution on its use in academic writing, see pros and cons.
- The prefix pro- (either hyphenated or fully amalgamated with another element) currently has several main groups of meaning.
- It is used with various titles to mean a person [or place] 'deputizing for' or 'standing in place of' the principal title-holder, as for example a pro-vice-chancellor in a University is an immediate subordinate to a Vice-Chancellor, the professional head of the institution; a proconsul in the Roman Empire was the Governor of a Province, exercising the powers of a Consul outside Italy, in his own territory - the term has been applied metaphorically to Governors, Viceroys etc in the British empire; a pro-cathedral is a church used as a temporary substitute for a Bishop's cathedral.
- It is frequently linked with the names of political parties or movements, causes or simple identities to mean '[one who is] in favour of', or 'supporting', the cause etc labelled by the second element, which may be a noun or an adjective. Examples include pro-Allied (often used of neutrals in the World Wars to indicate those who favoured the countries fighting Germany); pro-abortion to indicate those who support the rights of women to terminate unwanted pregnancies; pro-Russian, in general favouring the policies of Russia (this term was most common in the days of the USSR, and indicated a generally pro-Communist attitude).
- In Linguistics, pro- is prefixed to the names of grammatical elements to indicate a 'deputy' element used in place of the original, as a pronoun is a word that stands in for a noun.