role
The part or job someone or something has in a situation.
A role is the part you play or the job you do in a particular situation. When you act in a school play, your role might be the hero, the villain, or a talking tree. Each role has specific lines to say and actions to take. Outside of theater, everyone plays different roles throughout their day: you play the role of a student in class, a teammate at soccer practice, and a family member at dinner.
The word captures something important about how we function in groups. A good basketball team needs players in different roles: some focus on scoring, others on defense, and the point guard plays the role of organizing the offense. Each role matters, and the team works best when everyone understands and fulfills their part.
You can also talk about the role something plays in making something happen. Scientists might study the role of sleep in learning, or historians examine the role of the printing press in spreading ideas. Here, role means the function or contribution something makes to a larger outcome.