‘叹服’ is a compound verb meaning to admire deeply—so much so that one cannot help but sigh in awe. The first character 叹 (tàn) means 'to sigh' or 'to exclaim', often expressing strong emotion like wonder or reverence; the second character 服 (fú) means 'to submit', 'to be convinced', or 'to admire'. Together, they convey a visceral, emotionally charged admiration—not just intellectual approval, but heartfelt awe that moves you to sigh. It implies sincerity and intensity, stronger than mere ‘liking’ or ‘respect’.

This word is commonly used in formal writing, literary contexts, or thoughtful speech—especially when describing reactions to exceptional skill, wisdom, courage, or natural beauty. It’s not typically used for everyday preferences (e.g., food or fashion), but rather for profound human achievements or overwhelming natural phenomena. While it can appear in spoken Chinese, it carries a slightly elevated register and is more frequent in written descriptions of admiration.