Rank
suffix
The kanji and the word are exactly the same. That means they share meanings as well.
い
The reading is the on'yomi reading, which you learned. This is probably because you'll see this word attached to other words, showing the rank of that thing.
今年は何位だろう？
I wonder where I'll rank this year.
あのテニスプレイヤーは世界ランキング三位です。
That tennis player is ranked third in the world.
マラソンで一位になったので、両親がマウンテンバイクを買ってくれた。
I came in first in the marathon, so my parents bought me a mountain bike.