的
de
Expressing possession with "de"
的 is the possessive link — owner first, then 的, then what's owned.
Noun 1 + 的 + Noun 2
How it works
我的老师 (my teacher), 他的车 (his car), 王先生的公司 (Mr Wang's company). The order matches English's apostrophe-s, not the "of" construction.
的 does far more than possession later on — it also attaches adjectives and whole clauses to nouns — but ownership is where it starts.
Examples
wǒ de lǎo shī
我的老师
my teacher
zhè shì tā de shū
这是他的书。
This is his book.
nà shì shéi de shǒu jī?
那是谁的手机？
Whose phone is that?