This is the 3873rd most frequent Chinese word.
de
"De" (的) is a particle used to indicate possession, modification, or association.
Here, 'de' (的) is used to form a phrase '跑步的时候' (time of running), linking '跑步' (running) and '时候' (time).
我喜欢跑步的时候听音乐。
I like listening to music while running.
In this example, 'de' (的) connects the adjective '干净' (clean) with the noun '桌子' (table), describing the table.
她有一张干净的桌子。
She has a clean table.
In this sentence, 'de' (的) is used as a possessive marker to indicate ownership, linking '我' (I) with '书' (book).