This is the 138th most frequent Japanese word.
すぎ
"すぎ" means "too much" or "past" depending on context.
In this sentence, 'すぎ' is used to convey the idea of excessiveness, signifying 'too much,' followed by the verb '走る' (to run), creating '走りすぎる' (to run too much).
彼は走りすぎて疲れた。
He ran too much and got tired.
Here, 'すぎ' is again showing excess but applied to the verb '食べる' (to eat), creating '食べすぎる' (to eat too much).
朝食を食べすぎるとお腹が痛くなる。
If you eat too much breakfast, you will get a stomachache.
In this example, 'すぎ' is attached to an adjective, '小さい' (small), to create '小さすぎる' (too small), indicating a degree beyond suitable or proper.