‘无疑’ (wú yí) is an adverb meaning 'undoubtedly,' 'without doubt,' or 'beyond question.' It combines the characters 无 (wú), meaning 'not' or 'without,' and 疑 (yí), meaning 'doubt' or 'suspicion.' Literally, it means 'without doubt,' and functions to strongly affirm a statement’s certainty. It typically appears before a verb phrase or adjective, often at the beginning of a clause or after a subject, lending emphasis and conviction.

This word is common in formal writing, academic discussion, news reports, and persuasive speech — less frequent in casual conversation, where simpler expressions like 肯定 (kěndìng) or 当然 (dāngrán) may be preferred. It conveys intellectual confidence rather than emotional intensity, making it especially suitable for logical conclusions, factual assertions, or widely accepted truths.