Mr.Maru: What are you going to do today?

Sparky: I was thinking about going for a walk by 6.

Mr.Maru: Ok, how long are you going to be at home then?

Sparky: I'll be home by 4.

Mr.Maru: It's almost 4 now though.

Sparky: Yeah, I'm leaving at 4.

Mr.Maru: You mean you'll be home until 4.

Sparky: Right, I'll be home until 4. I'm leaving before the sun goes down.

How do you use until, by or before? What is the difference between these words? Let's go over some basic rules on how to use these.

Until – Basic Usage

We use the word 'until' to talk about a state or action that will continue to a certain point. For example,

I'm going to be at work until 6.
I'm studying every day until the test.

By – Basic Usage

We use the word 'by' to talk about an action or event that will happen in the future. This is not a continuous action or state. For example,

O The prints will be ready by 5.
X The prints will be ready until 5.

O We should be finished by 8.
X We should be finished until 8.

Be careful! Compare the two the differences of these two sentences:

George is going to be home by 9. (George is not home now, he will be home later.)
George is going to be home until 9. (George is at home now, he will leave later.)

Before – Basic Usage

We use the word 'before' to talk about how far into the future an event or action will be. For example,

There is only a month before summer vacation.
It's only a few minutes before my favorite show starts.

We can also use 'until' in this same situation:

There is only a month until summer vacation.
It's only a few minutes until my favorite show starts.

However, be careful with 'until' and 'before'. Using 'before' means that an action will happen no matter what happens, but 'until' means that an action usually has to meet a condition. For example,

Cook the meat until it turns brown. (Keep cooking the meat. The meat will turn brown because you are cooking it.)
X Cook the meat before it turns brown. (The meat will turn brown even if you don't cook it, but you have to cook it before it turns brown.)

This is a little complicated, so let's look at another example:

Take the laundry in before it rains. (You have to take in all the laundry before it rains.)
Take the laundry in until it rains. (Keep taking in the laundry. When it starts raining, stop taking in the laundry.)

Let's take a short quiz.

1) He was so tired today. He was in bed ____ 8pm.

A) until

B) by

C) before

2) I'm saving money ____ I can buy a new TV.

A) until

B) by

C) before

3) You need to fix that _________ the boss comes or he'll be angry.

A) until

B) by

C) before

Answers

1) B) – He completed the action of getting into bed by 8pm.

2) A) – I'm continuously saving money until I have enough money to buy a TV. It is a continuous action.

3) C) – You have to complete the action (fix something) before the boss comes. We can't use 'by' or 'until'.

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Can you make a sentence using by, until, or before? Try it in the comments below.