pro-

UK: /ˈprəʊ-/

Collins Concise English Dictionary © HarperCollins Publishers::

pro- prefix

1. in favour of; supporting: pro-Chinese
2. acting as a substitute for: proconsul, pronoun

Etymology: from Latin prō (adv and prep). In compound words borrowed from Latin, prō- indicates: forward, out (project); forward and down (prostrate); away from a place (prodigal); onward in time or space (proceed); extension outwards (propagate); before in time or place (provide, protect); on behalf of (procure); acting as a substitute for (pronominal); and sometimes intensive force (promiscuous)

pro- prefix

1. before in time or position; anterior; forward: prophase, procephalic, prognathous

Etymology: from Greek pro (prep) before (in time, position, rank, etc)

WordReference Random House Learner's Dictionary of American English © 2026

pro¹ /proʊ/   adv., adj., n., pl. pros. 
adv. 

1. in favor of an idea, proposal, etc.— adj. favorable:
   the pro side of the argument.

n. [countable]

2. the argument, position, or voter for something:
   the pros and cons.

Compare con¹.
pro² /proʊ/   adj., n., pl. pros. 
adj. 

1. Informal Terms professional:
   He turned pro last year.

n. [countable]

2. a professional:
   She's a real pro; she won't let you down.

pro-¹ ,[prefix.]

1. pro- comes from Latin, where it has the meaning "forward, forward movement or location;
   advancement'':
   proceed;
   prominent;
   promote;
   propose.
2. pro- is also attached to roots and words and means "bringing into existence'':
   procreate; produce.
3. pro- is also attached to roots and words and means "in place of'':
   pronoun.
4. pro- is also used to form adjectives that have the meaning "favoring the group, interests, course of action, etc., named by the noun;
   calling for the interests named by the noun'':
   pro- + choice → pro-choice (= in favor of allowing a choice to be made regarding abortions);
   pro- + war → prowar (= in favor of fighting a war).

pro-² ,[prefix.]

1. pro- comes from Greek, and has the meaning "before, beforehand, in front of'':
   proboscis;
   prophylactic;
   prothesis.
2. pro- is also attached to a word and means "primitive or early form'':
   prodrug; prosimian.

WordReference Random House Unabridged Dictionary of American English © 2026

pro¹  (prō), adv., n., pl. pros. 
adv. 

1. in favor of a proposition, opinion, etc.

n. 

2. a proponent of an issue;
   a person who upholds the affirmative in a debate.
3. an argument, consideration, vote, etc., for something. Cf. con ¹.

• Latin prō (prep) in favor of, for; akin to per-, Greek pró, Sanskrit pra
• Middle English 1350–1400

pro²  (prō), adj., n., pl. pros. [Informal.]
adj. 

1. Informal Terms professional.

n. 

2. Informal Terms professional.
3. the pros, the professional athletic leagues, as of football, baseball, or basketball:
   He's sure to be signed by the pros.

• shortened form 1840–50

pro³  (prō), n., pl. pros. [Slang.]

1. Drugs, Slang Terms prophylactic (def. 5).

• shortened form

pro  (prō; Eng. prō), prep. [Latin.]

1. Foreign Terms for.

PRO, 

1. public relations officer.

Also, P.R.O. 
Pro, [Biochem.]

1. Biochemistry proline.

pro-¹ ,

1. a prefix indicating favor for some party, system, idea, etc., without identity with the group (pro-British;
   pro-Communist;
   proslavery), having anti- as its opposite.
2. a prefix of priority in space or time having especially a meaning of advancing or projecting forward or outward, and also used to indicate substitution, attached widely to stems not used as words:
   provision;
   proceed;
   produce;
   protract;
   procathedral;
   proconsul.

• Latin prō-, pro-, combining form representing prō pro¹

pro-² ,

1. a prefix identical in meaning with pro- ¹, occurring in words borrowed from Greek (prodrome) or formed of Greek (and occasionally Latin) elements.

• Greek, combining form of pró for, before; see pro¹