在复合句中作状语的从句叫做状语从句。状语从句用来修饰主句中的动词、形容词或整个主句，说明时间、地点、原因、结果、目的、条件、让步、方式、比较等。
状语从句由从属连词引导。常见的状语从句有九种：
① 时间状语从句：when, while, as, before, after, until/till, since, as soon as 等；
② 地点状语从句：where, wherever；
③ 原因状语从句：because, since, as, now that 等；
④ 结果状语从句：so...that, such...that, so that；
⑤ 目的状语从句：so that, in order that, in case, for fear that 等；
⑥ 条件状语从句：if, unless, as long as, in case 等；
⑦ 让步状语从句：although, though, even though, even if, while, no matter how 等；
⑧ 方式状语从句：as, as if, as though；
⑨ 比较状语从句：than, as...as。
① 从句用陈述语序——与名词性从句一样，状语从句也必须用陈述语序。
✓ When he will come is unknown.
✗ When will he come is unknown.
② 主将从现——在时间状语从句和条件状语从句中，如果主句用一般将来时，从句要用一般现在时代替将来时。这是上海卷语法填空的最高频考点之一。
I will call you when I arrive.
If it rains tomorrow, we will stay at home.
③ 从句的位置——状语从句可放在主句之前或之后：
👉 口诀：状语从句用陈述，时间条件主将从现。
| 类型 | 常用连词 | 例句 |
|---|---|---|
| 时间 | when, while, as, before, after, until, since, as soon as | I will call you when I arrive. |
| 地点 | where, wherever | Where there is a will, there is a way. |
| 原因 | because, since, as, now that | He was late because he missed the bus. |
| 结果 | so...that, such...that, so that | He was so tired that he fell asleep at once. |
| 目的 | so that, in order that, in case | He got up early so that he could catch the bus. |
| 条件 | if, unless, as long as, in case | If it rains, we will stay at home. |
| 让步 | although, though, even if, while, no matter how | Although he is young, he knows a lot. |
| 方式 | as, as if, as though | He acted as if nothing had happened. |
| 比较 | than, as...as | He runs faster than I do. |
⭐ 核心提醒：时间和条件状语从句中，主句用将来时，从句用一般现在时代替将来时（主将从现）。
时间状语从句由下列连词引导：
· when：当……时（可指时间点或时间段）；
· while：在……期间（强调持续性，常与进行时连用）；
· as：当……时（强调"一边……一边……"，两动作同时发生）；
· before：在……之前；after：在……之后；
· until / till：直到……为止；
· since：自从……以来（主句用现在完成时，从句用一般过去时）；
· as soon as：一……就……；
· the moment, the minute, the instant：一……就……；
· hardly...when, scarcely...when, no sooner...than：刚一……就……（用于句首时，主句要部分倒装）。
① when / while / as 的区别：
| 连词 | 含义 | 从句谓语 |
|---|---|---|
| when | 当……时（点或段） | 一般过去时 / 过去进行时 |
| while | 在……期间（强调持续，或表对比） | 过去进行时（常） |
| as | 一边……一边……（同时发生） | 一般过去时 / 过去进行时 |
② since 的用法：
He has lived here since he came to this city.
It is three years since he joined the army.
③ hardly...when / no sooner...than 的倒装：
Hardly had I arrived when it began to rain.
No sooner had he left than the phone rang.
👉 口诀：Hardly/Scarcely 配 when，No sooner 配 than；主句过去完成，从句一般过去。
I will tell him the news as soon as he ____ (come) back.
📌 口诀：主将从现——时间、条件状语从句用一般现在时代替将来时。
He has lived here since he ____ (come) to this city.
📌 要点：since 从句用一般过去时，主句用现在完成时。
Hardly had I arrived ____ it began to rain.
条件状语从句由下列连词引导：
· if：如果；
· unless：除非（= if...not）；
· as long as / so long as：只要；
· in case：万一，以防；
· on condition that：条件是；
· provided / providing (that)：假如；
· suppose / supposing (that)：假设。
核心规则：主将从现——主句用一般将来时，条件状语从句用一般现在时。
If it rains tomorrow, we will stay at home.
I will not go unless he invites me.
① 主将从现（最高频考点）：
If it rains tomorrow, we will stay at home.
If you see him, tell him the news.
If you want to pass the exam, you must study hard.
② if 与 unless 的转化：
I will not go unless he invites me.
= I will not go if he doesn't invite me.
👉 口诀：条件从句主将从现；unless = if not，从句用肯定。
If it ____ (be) fine tomorrow, we will have a picnic.
📌 口诀：主将从现——条件从句用现在时。
Unless you ____ (not study) hard, you will fail.
📌 口诀：unless 从句用肯定，if not 从句用否定。
原因状语从句：由 because, since, as, now that 等引导。
· because：直接原因（语气最强，回答 why）；
· since：既然（已知原因，语气较弱）；
· as：由于（原因较明显）；
· now that：既然（口语中常用）。
结果状语从句：由 so...that, such...that, so that 引导。
· so + 形容词/副词 + that：He is so tall that he can reach the top.
· such + 名词短语 + that：He is such a good student that everyone likes him.
· so + 形容词 + a/an + 单数名词 + that：He is so good a student that everyone likes him.
目的状语从句：由 so that, in order that, in case, for fear that, lest 引导，从句谓语常用 can/could/may/might + 动词原形。
| 结构 | 用法 | 例句 |
|---|---|---|
| so + adj./adv. + that | so 后接形容词/副词 | He is so tall that he can reach it. |
| such + a/an + adj. + 单数名词 + that | such 后接名词短语 | He is such a good boy that everyone likes him. |
| such + adj. + 复数/不可数名词 + that | such 后接名词短语 | They are such interesting books that I want to buy them. |
| so + adj. + a/an + 单数名词 + that | so 后接"形容词+名词"组合 | He is so good a boy that everyone likes him. |
| so many / so much + 名词 + that | so 后接 many/much | There are so many books that I don't know which to choose. |
记忆技巧：
so many books / so much water（不能用 such many / such much）
so few books / so little water（不能用 such few / such little）
because / since / as 的区别：
He didn't come because he was ill.
Since you are free, let's go for a walk.
👉 口诀：so 后加形容词，such 后加名词；because 回答 why，since/as 表已知。
He is ____ clever that he can solve the problem.
📌 口诀：so + 形容词，such + 名词。
Because he was ill, so he didn't come.
📌 口诀：because 和 so 二者选其一，不能同时用。
He got up early so that he ____ (catch) the bus.
📌 要点：目的状语从句谓语用 can/could/may/might。
让步状语从句由下列连词引导：
· although / though：虽然（不能与 but 连用）；
· even though / even if：即使（语气更强）；
· while：虽然（放在句首，表示对比）；
· no matter how / what / who / when / where：无论……；
· however / whatever / whoever：无论……；
· as / though 引导让步从句时，从句要用倒装（形容词/副词/名词/动词原形 + as/though + 主语 + 谓语）。
① although / though 不能与 but 连用：
✓ Although he is young, he knows a lot.
✗ Although he is young, but he knows a lot.
英语中 although/though 与 but 不能同时使用（与汉语"虽然……但是……"的习惯不同）。
② as / though 引导让步从句的倒装：
把从句中的表语（形容词/名词）、状语（副词）或动词原形提前到 as/though 之前。
| 倒装成分 | 例句 |
|---|---|
| 形容词 + as + 主语 + 系动词 | Young as he is, he knows a lot. |
| 副词 + as + 主语 + 谓语 | Fast as he ran, he couldn't catch the bus. |
| 名词 + as + 主语 + 系动词（不加冠词） | Child as he is, he knows a lot. |
| 动词原形 + as + 主语 + 助动词 | Try as he might, he couldn't solve the problem. |
③ no matter how 与 however 的互换：
No matter how hard he tried, he failed.
= However hard he tried, he failed.
👉 口诀：although 不与 but 连用；as/though 引导让步要倒装。
Although he is rich, but he is not happy.
📌 口诀：although 与 but 不共戴天。
As he is young, he knows a lot.（表达"虽然他年轻"）
📌 要点：as 表示"虽然"时必须倒装，表示"因为"时不倒装。
方式状语从句：由 as, as if, as though 引导。
Do as I told you.
He acted as if nothing had happened.
比较状语从句：由 than, as...as, not so...as 引导。
He runs faster than I do.
He is as tall as his father.
地点状语从句：由 where, wherever 引导。
Where there is a will, there is a way.
Wherever you go, I will follow you.
① as if / as though 的虚拟语气：
He acts as if he were the boss.（与现在相反）
He acted as if he had known the truth.（与过去相反）
② 比较状语从句中的"省略"：
He runs faster than I do.（= than I run）
He is as tall as his father (is).
③ 地点状语从句 vs 定语从句：
| 类型 | 例句 | where 的作用 |
|---|---|---|
| 地点状语从句 | Where there is a will, there is a way. | 引导从句，修饰主句 |
| 定语从句 | This is the house where I lived. | 引导从句，修饰 the house |
👉 口诀：where 前有先行词 → 定语从句；where 前无先行词 → 地点状语从句。
I will call you when I ____ (arrive).
📌 口诀：主将从现，时间条件都适用。
He has lived here since he ____ (come) to this city.
Hardly had I arrived ____ it began to rain.
📌 口诀：Hardly/Scarcely 配 when，No sooner 配 than。
Because he was ill, so he didn't come.
Although he is rich, but he is not happy.
He is ____ clever that he can solve the problem.
📌 口诀：so + 形容词，such + 名词。
As he is young, he knows a lot.（想表达"虽然他年轻"）
📌 要点：as 表"虽然"要倒装，表"因为"不倒装。
He got up early so that he ____ (catch) the bus.
📌 要点：目的状语从句用 can/could/may/might。
上海卷对状语从句的考查主要集中在：
状语从句每年为上海卷直接贡献 3—5 分，是语法填空和中译英的"得分利器"。