过去某一时间点之前已经完成的动作
（“过去的过去”）。
By the time I arrived, the movie had started.
过去某一时刻正在进行的动作。
I was reading a book at 8 p.m. yesterday.
过去发生的动作或状态（与现在无关）。
I visited Beijing last year.
表示习惯性动作：
I go to school every day.
表示客观事实或真理：
The sun rises in the east.
表示现在的状态或特征：
She loves reading books.
表示正在进行的动作：
I am reading a book now.
表示现阶段正在发生但未必此刻进行的动作：
She is studying for her exams this week.
表示计划或安排好的未来事件：
We are leaving for Beijing tomorrow.
过去发生的动作对现在有影响或持续到现在。
I have finished my homework.
将来要发生的动作或状态。
I will visit my grandparents tomorrow.
时间状语
by the time（到……时为止）
By the time I arrived, the movie had started.
before/after（在……之前/之后）
He had left before I called him.
by + 过去时间点（截至……）
She had finished the report by 9 p.m.
体现“过去的过去”，常与一般过去时搭配使用。
at this time yesterday（昨天此时）
I was studying at this time yesterday.
when/while（当……时，常与一般过去时连用）
She was cooking when the phone rang.
from…to…（从……到……）
He was working from 8 a.m. to 5 p.m.
持续信号词（用于进行时）：
all day/night（整天/整夜）
They were working all day.
yesterday（昨天）
I finished my homework yesterday.
last week/month/year（上周/上个月/去年）
She visited Beijing last summer.
…ago（……前）
He left two hours ago.
in 2020（在2020年）
The event happened in 2020.
just now（刚才）
They called me just now.
always（总是）
usually（通常）
often（经常）
sometimes（有时）
every day/week/year（每天/周/年）
on Sundays（在周日）
频率副词（用于一般现在时）：
sometimes（有时）、often（经常）、seldom（很少）
He often plays basketball after school.
now（现在）
at the moment（此刻）
right now（现在）
these days（这些天）
Look!/Listen!（看！/听！）
already（已经）
I have already read this book.
yet（尚未，用于否定/疑问句）
Have you finished yet?
ever/never（曾经/从未）
Have you ever been to Paris?
since + 时间点（自从……）
She has lived here since 2010.
for + 时间段（持续……）
They have studied for three hours.
阶段性时间（常用于现在完成时）：
recently（最近）、lately（近来）
I have seen her recently.
tomorrow（明天）
We will have a test tomorrow.
next week/month/year（下周/下个月/明年）
They are going to travel next month.
in the future（未来）
Robots will help humans in the future.
soon（很快）
The meeting will start soon.
in + 时间段（在……之后）
The train arrives in 10 minutes.
