Pro has 13 different meanings across 6 categories:
an athlete who plays for pay
"After years of playing basketball just for fun, Marcus finally signed a contract and became a pro last summer."
an argument in favor of a proposal
"During the meeting, she presented several pro arguments to convince the board that we should approve the new budget."
An advantage of something, especially when contrasted with its disadvantages (cons).
"The new filtration system uses pro technology to remove contaminants from the water supply."
A professional sportsman.
A prostitute.
A proproctor.
Initialism of pressure retarded osmosis.
In plain English: A pro is someone who is very skilled at doing something because they do it for money or as their main job.
"The pro argued that we should approve the new plan."
Usage: As a noun in everyday conversation, "pro" is short for professional and refers to someone who works in a specific field as their main job or an expert at a particular activity. Do not use this term when referring to the technical acronym for pressure retarded osmosis, which is unrelated to common usage.
Professional.
"The pro golfer missed his putt on the final hole of the tournament."
In plain English: Pro means being in favor of something or supporting a particular side in an argument.
"The pro team won the game easily."
Usage: Use "pro" as an adjective to mean professional or skilled in a specific field, often contrasting with amateur status. It typically appears before a noun, such as in "pro athletes" or "pro equipment," to indicate high-level competence.
in favor of a proposition, opinion, etc.
"She cast her vote pro during the debate on raising the minimum wage."
In favor of.
"The company decided to go pro for renewable energy after years of debating against it."
A surname, from Spanish​.
"The new pro at our local gym has a reputation for being very strict about form."
A theoretical phonologically null pronoun
"In generative grammar, linguists posit that a pro occupies the subject position in pro-drop languages like Italian without being overtly pronounced."
The word pro entered English during the Late Middle Ages directly from Latin. In its original form, it meant "on behalf of."