To remain; to be left over; to be in excess; to be too many—used intransitively to indicate something remains or is surplus.
ラーメンを作りすぎて、スープが余った。
I made too much ramen; there was leftover broth.
時間が余ったから、買い物に行った。
I had extra time, so I went shopping.
余るほどお金があれば旅行したい。
If I had money to spare, I'd travel.