Chinese Basic 1
First contact

The use of 的 as an attribute marker

de is the most common word in Chinese. It is frequently used as a grammatical marker to link a noun and its modifier.
For example, in 这是我的名片 (Zhè shì wǒ de míngpiàn), This is my name card, the grammatical marker links the noun 名片 with the modifier indicating possession, i.e. my name card.

Similarly in 我的母语 (wǒ de mǔyǔ) my mother tongue, the noun 母语 is modified by indicating whose language the phrase is about.