a person who takes the lead or acts as a pioneer in a certain field or activity

The sheep that leads a flock; (figuratively) a person, organization, or thing that leads a group or sets a trend

An expert with a high level of academic knowledge who leads and guides others in a specific field of scientific research; a pace-setter in an academic discipline.

a pioneering example; a leading role in a movement or task

person who takes the lead or acts as a foreman