之 (zhī) is classical Chinese's 的, and it survives everywhere in modern fixed patterns. The big one is 之一 "one of…": 北京是中国最大的城市之一 "Beijing is one of China's largest cities" — the standard partner of superlatives.
It also builds every fraction and percentage: 百分之七十 "70%", 四分之一 "a quarter" — literally "of a hundred, seventy." Don't go replacing everyday 的 with 之, though; outside these patterns it sounds like you've wandered out of an ancient poem.
Practice this pattern in graded stories like Atomic Habits: One Percent Better (Part 1), Fire and Anger, The Death of Mrs. Fan (Part 1) inside the Literate Chinese app.
Every grammar point in this guide is built into the Literate Chinese app, with graded stories that use the pattern naturally and flashcards matched to the words you know — in Mainland or Taiwan Mandarin. Free on iOS and Android.