/ɑˈpəʊnənt/ – Noun
Definition: Đối thủ hoặc bên đối đầu.
A more thorough explanation: 1. a person who disagrees with an idea, project, or a plan etc and who tries to change or stop it
2. a person who is arguing, fighting, or competing against you
Example: 1. Opponents have criticized the plan because of its environmental impact.
2. He is a noted human rights campaigner and an opponent of the President.