The phrase "a main competitor" is correct and usable in written English.
It can be used when referring to a primary rival in a business or competitive context.
Example: "In the tech industry, Company A is considered a main competitor to Company B due to their similar product offerings."
Alternatives: "a key rival" or "a primary competitor".
Among nonluxury brands the Ford Edge has turned out to be a main competitor.
Netflix has identified it as a main competitor; that company's chief executive, Reed Hastings, recently called the HBO Go product "quite impressive".
Not long after that attack, a gunman in a black ski mask shot and killed Vladimir Kanevsky, a Russian billboard mogul and head of the outdoor advertising agency Big Board Group, a main competitor of News Outdoor.
At large, these lead to a situation that the expressways are becoming a counterpart to and eventually a main competitor of the conventional railway.
Known for its thick and protective casing, OtterBox is a main competitor in the iPhone case space.
When IBM bought Informix [formerly a main competitor to Oracle in the database market], they paid less than the combined value of Informix's last two acquisitions, which should tell you something about the state of that company.
Braathens rejected a proposal from the main competitor Scandinavian Airlines System SASS) for a merger; instead the helicopter division was sold and the company listed on the Oslo Stock Exchange.
With his waspish movement, the 29-year-old certainly provides a more subtle threat than André, his main competitor for a starting role.
TalkSport today launched a fresh attack on its main competitor, the BBC, filing an official complaint to media regulator Ofcom that Radio 5's exclusive deal with the Football Association is anti-competitive.
In what looks like a cruel joke, its main competitor, ImageShack (the company behind the yFrog Twitter photo hosting service), went ahead and filed to trademark the name "Twitpic" before Twitpic did.
-Create an imaginary car that your group wishes to market, along with the payment plan for this car, and an imaginary car that is your car's main competitor, with a different payment plan.
