骤然 (zhòu rán) is an emphatic literary adverb meaning 'suddenly' or 'all of a sudden', conveying a sharp, unexpected, and often dramatic change in situation, emotion, or event. The character 骤 means 'sudden' or 'hasty'—originally linked to the rapid gait of a horse—and 然 functions as a classical suffix meaning 'in such a manner', reinforcing the adverbial quality. Together, they form a compound that emphasizes abruptness with a tone of gravity or intensity, making it common in formal writing, literature, news reports, and emotional narration.

Unlike the more neutral and colloquial 突然 (tūrán), 骤然 carries heightened stylistic weight and is rarely used in casual speech. It frequently modifies verbs describing changes in weather, mood, health, or social circumstances—e.g., 骤然降温 (a sudden temperature drop), 骤然离世 (to pass away unexpectedly). Its literary flavor makes it unsuitable for everyday conversation but highly effective in descriptive or dramatic contexts where emphasis on immediacy and impact is desired.