Adverbs / 副词

HSK 4 突然 vs 忽然

sudden — one is also an adjective, the other is adverb-only

Comparison / 对比

突然 tūrán忽然 hūrán
Part of speechAdj. AND adv.: 很突然的变化Adverb only: ×很忽然
Can use 很?Yes: 来得很突然No: ×很忽然
As attributiveYes: 突然的消息No: ×忽然的消息
As adverb他突然站起来他忽然站起来 (same)

Examples / 例句

突然: 这场雨来得很突然。
Zhè chǎng yǔ lái de hěn tūrán.
This rain came very suddenly. (突然 as adj. with 很)
忽然: 她忽然想起了一件重要的事。
Tā hūrán xiǎng qǐ le yí jiàn zhòngyào de shì.
She suddenly remembered something important. (忽然 as adverb)
Quick rule: When used as an adverb before a verb, they are interchangeable. The difference: 突然 can also be an adjective (很突然, 突然的变化), but 忽然 CANNOT. If you see 很___ or ___的+noun, it must be 突然.

Fill in the Blank / 填空练习

Type the correct word to complete each sentence. Press Enter or click Check.

他的决定来得很，我们都没准备。
走着走着，下起了大雨。
这是一个非常的变化。

Quick Quiz / 小测验

这件事发生得太了，大家都没准备。
With 得 + degree = adjective use → only 突然 works.
走着走着，下起了大雨。
Adverb before verb — both work, but 忽然 is more natural for narrative flow.
这是一个非常的决定。
Modifying a noun (___的+noun) = adjective → only 突然.

Real HSK 4 Test Questions Using 突然 or 忽然 / 真题示例

2 actual HSK 4 questions from our mock exams that test the 突然 vs 忽然 distinction:

From HSK 4 Mock Test 01 · Q80
森林里，动物们决定举办一个晚会，这次演出吸引了几乎所有的动物。他们都很积极，准备的节目各有特点，小鸟要给大家唱歌，老虎要跳舞，小猫要画画儿，猴子要讲故事，狮子说他给大家照相，熊猫说：我不会表演，但是我可以当观众，为大家鼓掌。"
最后只剩下小牛了，她想了好久，忽然得意地说："我负责为大家送免费的牛奶！"

★ 谁打算为大家讲故事？
A 狗B 马C 猴子 ✓D 小猪
From HSK 4 Mock Test 01 · Q81
森林里，动物们决定举办一个晚会，这次演出吸引了几乎所有的动物。他们都很积极，准备的节目各有特点，小鸟要给大家唱歌，老虎要跳舞，小猫要画画儿，猴子要讲故事，狮子说他给大家照相，熊猫说：我不会表演，但是我可以当观众，为大家鼓掌。"
最后只剩下小牛了，她想了好久，忽然得意地说："我负责为大家送免费的牛奶！"

★ 小牛负责为大家：
A 报名B 送牛奶 ✓C 填写地址D 小猪

突然 vs 忽然 FAQ

Are 突然 and 忽然 interchangeable in HSK 4?

No. Although 突然 (tūrán) and 忽然 (hūrán) translate similarly into English, HSK 4 fill-in-the-blank and listening questions test exactly the distinction between them. When used as an adverb before a verb, they are interchangeable.

How is 突然 vs 忽然 tested in HSK 4?

Most often in HSK 4 阅读 (reading) Part 1 选词填空 (Q46-55), where you choose the correct word for a blank in a sentence. Also appears in 听力 (listening) where the speaker uses one but the printed answer paraphrases with the other. Master both 突然 and 忽然 collocations to lock in these points.

What's the quickest way to remember 突然 vs 忽然?

When used as an adverb before a verb, they are interchangeable. The difference: 突然 can also be an adjective (很突然, 突然的变化), but 忽然 CANNOT. If you see 很___ or ___的+noun, it must be 突然. Practice 3-5 fill-in-blank questions in our HSK 4 mock exams to lock the distinction.

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Use this HSK 4 distinction in real test conditions

⚡ Strategy
HSK 4 选词填空 (Q46-55) tips
📝 Patterns
100 essential HSK 4 sentences
🔧 Grammar
HSK 4 grammar guide (14 topics)
🎯 Practice
12 HSK 4 mock exams