1
the suddenness of [noun]
suddenness 常与 the 连用，后接 of 说明突然发生的事件。
The suddenness of the storm surprised everyone.
暴风雨的突然让每个人都感到意外。
突然；意外
先理解核心含义，再看它在真实句子里的用法。
突然；意外
the quality of happening with headlong haste or without warning
The suddenness of the storm surprised everyone.
暴风雨的突然让每个人都感到意外。
突然；意外
The state of being sudden.
The suddenness of the storm caught everyone off guard.
暴风雨来得突然，让大家都措手不及。
She was startled by the suddenness of his departure.
她被他突然的离开吓了一跳。
The suddenness with which they changed the plan left us confused.
他们突然改变计划，把我们搞糊涂了。
suddenness 常与 the 连用，后接 of 说明突然发生的事件。
The suddenness of the storm surprised everyone.
暴风雨的突然让每个人都感到意外。
with a suddenness that 强调动作发生得令人意外，that 后接完整句子。
He stopped with a suddenness that startled us.
他停下来的那种突然让我们吓了一跳。
the suddenness with which 引导定语从句，说明某事件发生的突然程度。
The suddenness with which the news spread was remarkable.
消息传播之突然令人惊叹。
Not this
The sudden of the storm frightened everyone.
Use this
The suddenness of the storm frightened everyone.
这里需要名词作主语，而“sudden”是形容词；应改为名词“suddenness”（突然性），并保留“the suddenness of”结构来表示“……的突然”。
Not this
I was shocked by the suddenly of his decision.
Use this
I was shocked by the suddenness of his decision.
介词“by”后需接名词，不能用副词“suddenly”；应改为名词“suddenness”，并搭配“of his decision”表示“他决定的突然性”。
Not this
The accident happened with sudden and no warning.
Use this
The accident happened with suddenness and no warning.
介词“with”后需接名词作宾语，“sudden”是形容词，不能作宾语；应改为名词“suddenness”，与“with”搭配表示“突然地”。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
变化的突然
The suddenness of the change made it hard to adjust.
变化的突然让人难以适应。
突然地，出其不意地
The door slammed shut with suddenness.
门砰地一声突然关上了。
令人吃惊的突然
The machine stopped with startling suddenness.
机器突然停了下来，令人吃惊。
她离开的突然
The suddenness of her departure left us all confused.
她突然离开让我们都摸不着头脑。
意想不到的突然
The decision came with unexpected suddenness.
这个决定来得意想不到地突然。
Use suddenness naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
sudden（突然）+名词后缀-ness，就是“突然、意外”；联想事情猝不及防地发生。
语域：neutral 常见场景：news reports、literary narration、formal essays suddenness 是抽象名词，多用于书面叙述、文学或正式讨论；日常口语中较少单用，常用 the fact that it happened so suddenly 或 how sudden it was 来表达。总体语气中性，略带正式感。
这些词都含透明的后缀 -ness，读作 /nəs/（或 /nɪs/）。但它们的重读元音各不相同，因此都不与 suddenness /ˈsʌdnnɪs/ 押韵。注意：suddenness 拼写中有两个 n，重读为 /ʌ/；不要与 sadness /ˈsæd-/、darkness /ˈdɑːrk-/ 等混淆，它们拼写相近但发音不同。
Dictionary facts from ECDICT, WIKTIONARY.