‘唯恐’ is a classical and formal conjunction meaning 'fear lest' or 'dread that', expressing intense anxiety about a possible negative outcome. Though composed of two characters—唯 (wéi), meaning 'only' or 'solely', and 恐 (kǒng), meaning 'to fear'—together they form an idiomatic expression indicating the speaker’s deep concern that something undesirable might happen. It conveys a sense of urgency and precaution, often implying that the subject takes action to prevent the feared event.

This word appears frequently in written Chinese—especially in essays, news reports, and formal speech—but is rare in casual spoken conversation. It typically introduces a subordinate clause beginning with ‘唯恐 + [subject] + [verb phrase]’, and is almost always followed by a negative or undesirable result. Its tone is serious and somewhat literary, lending gravity to warnings, precautions, or expressions of vigilance.