adjective / adverb
foremost
FOR-mohst/ˈfɔːrməʊst/
Ahead of all others in position or importance.
The foremost climber leads the others up the mountain.

Etymology
Old English formest covered both being first and being most prominent. That pairing connects a leading position with the highest importance or greatest advancement.
In context
this astronomer Lincoln laaz is very important because he was one of the world's foremost authorities on meteors
More examples
- She is one of the nation's foremost experts on earthquakes.
- First and foremost, we need a plan everyone understands.
- The foremost runner reaches the bridge a few seconds ahead.
Forms
foremost