The foremost thing or person in a group is the most important or best.
He was one of the world's foremost scholars of ancient Indian culture.
他是世界上最优秀的古印度文化学者之一。
first and foremost
You use first and foremost to emphasize the most important quality of something or someone.
It is first and foremost a trade agreement.
它首先是一项贸易协定。