完全 (wán quán) is an adverb meaning 'completely' or 'entirely'. Though both characters individually carry meanings—'完' suggests completion or wholeness, and '全' means 'whole' or 'all'—together they function as a fixed, inseparable adverbial phrase. It emphasizes totality with no exceptions or partiality, often intensifying verbs, adjectives, or stative predicates. It’s commonly used in formal and informal speech alike, especially when asserting absolute agreement, certainty, absence, or fulfillment.

The word frequently appears before verbs (e.g., 完全理解), adjectives (e.g., 完全正确), or nouns with 的 (e.g., 完全的可能性). Unlike some other intensifiers, 完全 cannot be reduplicated or modified by degree words like 很 or 非常—it stands alone to convey fullness of state or action. It’s neutral in register and widely appropriate across contexts, from academic writing to everyday conversation.