/ rəʊl; NAmE roʊl/ noun
1.
the function or position that sb has or is expected to have in an organization, in society or in a relationship :
the role of the teacher in the classroom
She refused to take on the traditional woman's role.
In many marriages there has been a complete role reversal (= change of roles) with the man staying at home and the woman going out to work.
2.
an actor's part in a play, film / movie, etc. :
It is one of the greatest roles she has played.
Who is in the leading role (= the most important one) ?
3.
the degree to which sb/sth is involved in a situation or an activity and the effect that they have on it :
the role of diet in preventing disease
The media play a major role in influencing people's opinions.
a key / vital role
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WORD ORIGIN
early 17th cent.: from obsolete French roule roll, referring originally to the roll of paper on which the actor's part was written.