“忽然” and “突然” both mean “suddenly” in English and are often interchangeable — but there are subtle differences in usage, formality, and tone.
忽然 (hūrán) vs 突然 (tūrán)
1. Meaning
Both mean:
Suddenly, unexpectedly, all of a sudden
They describe a quick or unexpected change, often in events or emotions.
2. Grammatical Use
| Word | Part of Speech | Position in Sentence | Example |
|---|---|---|---|
| 忽然 | Adverb only | Before verb | 他忽然笑了。(He suddenly laughed.) |
| 突然 | Adverb OR Adjective | Before verb / as modifier | 他突然站起来了。(He suddenly stood up.) 这是一个突然的决定。(This is a sudden decision.) |
3. Tone & Style
| Word | Style | Usage Frequency | Notes |
|---|---|---|---|
| 忽然 | Slightly literary/formal | Less common in spoken Chinese | Often seen in writing or narration |
| 突然 | Neutral & very common | Very frequent in both spoken and written Chinese | More flexible in grammar |
4. Examples
忽然 (Adverb only)
天空忽然变黑了。
→ The sky suddenly turned dark.他忽然不说话了。
→ He suddenly stopped talking.
突然 (Adverb & Adjective)
我们走着走着，突然下雨了。
→ As we were walking, it suddenly rained.这是一个突然的消息。
→ This is sudden news.
Summary:
| Comparison | 忽然 | 突然 |
|---|---|---|
| Meaning | suddenly | suddenly |
| Part of Speech | adverb | adverb or adjective |
| Style | more literary | neutral, more common |
| Example (adv) | 他忽然笑了。 | 他突然站起来了。 |
| Example (adj) |  (not used as adj) | 突然的变化 (a sudden change) |
Tip to Remember:
If you’re speaking or writing casually: use 突然.
If you’re writing a story or a formal essay: you might use 忽然 for a literary feel.