地

The pattern is fixed: Adjective + 地 + Verb. The particle marks the preceding word as describing HOW the verb is performed — the Chinese equivalent of English -ly: 慢慢地走 (walk slowly), 高兴地笑 (laugh happily), 仔细地听 (listen carefully), 默默地看 (watch silently). Reduplicated adjectives like 慢慢, 轻轻, 深深 are especially common in this slot.

Three particles share the sound de but differ in role: 的 links modifier to noun (我的车), 得 links verb to result or degree (跑得快), 地 links adverb to verb (慢慢地走). All three sound identical in speech; readers tell them apart only in writing. When the slot before the verb is an adjective describing manner, use 地.

Originally read dì 'earth / place'. The adverbial particle reading toneless de arose around the Tang–Song period when 地 was grammaticalised from a locative-style suffix ('at the place of doing X') into a pure manner marker. Modern Mandarin keeps both readings: the noun dì for any reference to earth or place, and the particle de purely after an adverbial modifier.