These small words put events in order and set limits in time. The hard part is choosing between pairs that look alike, like until and by, or during and while. Each one has a simple test you can use.
The pattern
Please finish the report by Friday.
I'll wait here until 6:00.
My phone rang while I was driving.
01Until or by?
Until means an action or situation continues up to a point, and then stops: stay, wait, work, be open until 6:00.
By is a deadline. It means "at that time or earlier." It goes with actions that happen once: finish, send, pay, arrive by Friday. Test: if you can say "no later than," use by.
With not, until tells you when something starts: "The store doesn't open until 10:00." In casual speech and texts, Americans also say till.
- I'll be at the gym until 7:30.
- Please pay the rent by the first.
- Can you send it by noon?
- We didn't eat until 9:00.
02During, for or while?
All three talk about a period of time, but they take different words after them.
- I fell asleep during the movie.
- We talked for three hours.
- She called while I was in the shower.
| Word | What comes after | Example |
|---|---|---|
| during | a noun: an event or period | during the meeting |
| for | a length of time | for two hours |
| while | subject + verb | while I was cooking |
03Before and after
Use before and after with a noun, with an -ing form, or with a full clause. When the clause is about the future, use the present tense after before and after, not will.
- Let's grab lunch after the meeting.
- Check your email before leaving work.
- After I finish this, I'll call you.
- Before you sign the lease, read it carefully.
04Through: the American way
Americans say Monday through Friday to mean from Monday to Friday, including Friday. Through also marks the last day of something: "The sale runs through Sunday" means Sunday is included. This makes through clearer than until when you need to say the last day counts.
- The office is open Monday through Friday.
- Our hotel is booked through the 14th.
- I'm on vacation June 3 through June 10.
05Common mistakes
I have to finish this until Friday.
I have to finish this by Friday.
A deadline for a one-time action takes by.
I slept during eight hours.
I slept for eight hours.
A length of time takes for.
During I was in college, I worked at a bank.
While I was in college, I worked at a bank.
Subject + verb comes after while, not during.
Call me before you will leave.
Call me before you leave.
Use the present tense after before and after, even for the future.