英语语法，一次学一点
每个语法点都用几句话讲清楚，并在小故事里练习：先看到它怎么用，再动手做题。
A1 入门
- 冠词 a / an / the (Articles)第一次提到一个可数名词时用 a 或 an：I have a dog. 元音音素开头的词前用 an：an apple, an hour。说话双方都知道是哪一个时用 the：The dog is in the garden. 泛指复数或不可数名词时通常不用冠词：I like cats.
- 现在进行时 (Present continuous)现在进行时表示此刻正在发生的事：Look! It is raining. 结构是 am / is / are + 动词-ing。它也可以表示最近一段时间正在做的事：I am learning English this year.
- 一般现在时 (Present simple)一般现在时表示习惯、经常发生的事和事实：I drink tea every morning. 主语是 he / she / it 或单数名词时，动词要加 -s 或 -es：She works. He watches TV. 否定和疑问用 do / does：I don't like coffee. Does he live here?
- There is / There are（某处有……）There is / There are 表示“某处有某物”：There is a park near my home. 单数或不可数名词用 there is，复数名词用 there are：There are three books on the table. 否定：There isn't any milk.
A2 初级
- 比较级和最高级 (Comparatives and superlatives)比较两个事物用比较级：短形容词加 -er，长形容词前加 more，后面用 than：Tom is taller than Ben. This book is more interesting than that one. 三个或以上比较用最高级：the + -est 或 the most：the tallest, the most beautiful。不规则：good → better → best, bad → worse → worst。
- 将来时 will / be going to (Future)be going to 表示已经计划好的事或有迹象要发生的事：I'm going to visit my aunt on Sunday. Look at the clouds, it's going to rain. will 表示临时决定、预测和承诺：I'll help you. I think she will win.
- 一般过去时 (Past simple)一般过去时表示过去某个时间发生并已经结束的事：I visited Beijing last year. 规则动词加 -ed：walk → walked；很多常用动词是不规则的：go → went, see → saw, have → had。否定和疑问用 did + 动词原形：I didn't see him. Did you call her?
B1 中级
- 第一条件句 (First conditional)第一条件句表示将来很可能发生的情况及其结果：If it rains, we will stay at home. if 从句用一般现在时，主句用 will + 动词原形。if 从句在前时，后面加逗号。
- 被动语态 (Passive voice)被动语态把动作的承受者放在句子开头，用于不知道、不重要或不想说是谁做的时候：Tea is grown in Yunnan. The bridge was built in 1990. 结构是 be + 过去分词；要说明做动作的人时用 by：The book was written by a young teacher.
- 过去进行时 (Past continuous)过去进行时表示过去某一时刻正在进行的事：At eight o'clock I was having dinner. 常和一般过去时一起用：较长的背景动作用过去进行时，突然发生的短动作用一般过去时：I was walking home when it started to rain.
- 现在完成时 (Present perfect)现在完成时把过去和现在连在一起：表示到现在为止的经历（I have been to Shanghai.）、刚完成并影响现在的事（She has lost her key.）、从过去持续到现在的事（We have lived here for five years.）。结构是 have / has + 过去分词。有具体的过去时间（yesterday, in 2020）时用一般过去时。
B2 中高级
- 定语从句 (Relative clauses)定语从句放在名词后面修饰它（中文的定语放在名词前面）：the man who lives next door（住在隔壁的那个人）。指人用 who，指物用 which，人和物都可以用 that。表示“……的”用 whose：the girl whose bike was stolen。
- 间接引语 (Reported speech)转述别人说过的话时，时态通常往过去推一步：“I am tired.” → She said (that) she was tired. “We will come.” → They said they would come. 人称和时间词也要跟着变：today → that day, tomorrow → the next day。转述问题时用陈述语序：He asked where I lived.
- 第二条件句 (Second conditional)第二条件句表示现在或将来不太可能、或与事实相反的假设：If I had more time, I would learn the piano. if 从句用一般过去时，主句用 would + 动词原形。正式英语中 be 动词常用 were：If I were you, I would wait.