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A detailed guideline on the usage and differentiation between When and While

In English, when we want to express events related to time, we often think of When and While. The questions arise: "When do we use 'When'?" and "When do we use 'While'?" or "What are the formulas for 'When' and 'While' in English?" PREP will answer all of these in this article. Let's refer to it right away!

I. What is When?

What is When? When is an English conjunction, used to create sentences about time, events, or conditions that have a connection between clauses. It is also used to indicate the time when an event, condition, or action happens after another event, condition, or action.

For example:

When I go to the gym, I always do some cardio exercises.
When she arrived at the party, she greeted everyone with a smile.
When they have finished their homework, they can watch a movie.

II. What is While?

What is While? While is an English conjunction used to create sentences about two actions happening simultaneously. While typically serves as a connector to combine two actions or events occurring at the same time. For example:

While she is studying in her room, her brother is playing video games in the living room.
I read a book while you were drying your hair.

III. The position of when and while in a sentence

In English, the position of When vs. While can vary depending on the context and the intended meaning you want to convey. Let's quickly explore the positions of When and While in English sentences. Take a look:

The position of When in a sentence:
- At the beginning of a sentence (to start the sentence), for example: When I arrived at the station, the train had already left.
- In the middle of a sentence (to indicate time, event, or condition), for example: I usually go for a run in the morning when the sun is rising.
The position of while in a sentence:
- Before the first clause (when one action interrupts another), for example: While I was doing my homework, my mother called me.
- In the middle of a sentence (to indicate two actions happening simultaneously), for example: She is listening to music while her sister is reading a book.

The position of when and while in a sentence

IV. The usage of When and While in English

In addition to understanding the concepts of When and "While", it's important to know how these two words are used. Let's explore how to use When and While in each grammar structure below with PREP!

1. While

Structure	Usage	Example
While + Simple Present, Simple Present	To express two simultaneous and ongoing events that occur over a period of time	While I study at home, I listen to music and TV.
While + Past Continuous, Simple Past	To express an action that was happening in the past while another action occurred	While I was reading a book, the phone rang.

2. When

Structure	Usage	Example
When + Simple Present, Simple future	To express the relationship between an action and its result or a future event,	When he finishes his work, he will go to the gym.
When + Simple Past, Past Perfect	To express an action that occurs before the action in the When clause	When she arrived at the party, the cake had already been eaten.
When + Simple Past, Simple Past	To express two actions happening close to each other or in immediate succession	When I finished breakfast, I dressed for school.
When + Past Continuous – (clear point of time), Simple Past	To express one action happening while another action takes place	When I was having breakfast, the phone rang.
Hardly/ Scarcely + had + S + PII (Past Participle)… when + S + V-ed.	Furthermore, the When structure can also be used in an inverted sentence, which means "Just as... then...".	Hardly had I started reading the book when the phone rang.

V. The difference between when and while

Let’s discover the similarities and differences between While and When in the below table provided by PREP!

Criteria		When	While
Similarities		Both When and While are used to combine events or actions in a sentence to express a time relationship. When there is one clause in the present simple tense and another clause in the present continuous tense, both When and While can be used. (Note: If the first clause is in the present continuous tense and the second clause is in the present simple tense, only When can be used, not While).
Differences	Time	When is often used to indicate a specific or exact moment when an event occurs. For example: When I came home, it was exactly 12 AM. When is used to describe two separate actions happening consecutively. For example: She was mad at me when I broke her favorite photo frame.	While is often used to indicate a period that is ongoing, without necessarily being specific. For example: While I was having breakfast, he was working. While is used to describe two actions happening simultaneously. For example: I was putting away the dishes while my friend was doing the laundry.
	Meaning	When is often used to emphasize the main event. For example: When I finish my homework, I will watch a movie ➞ Main event	While typically places emphasis on both events happening simultaneously. For example: While I was studying, my sister was playing the piano.

VI. Exercises on when and while with detailed answers

To avoid confusion in the usage of When and While in English, it is important to not only study the theory but also practice through exercises. Below, PREP provides some questions for you to actively complete and check the answers below:

Exercise: Fill in the blank with when or while

_______ the bus arrives, we’ll get on.
I thought I heard him come in _______ we were having dinner.
_______ I reached the cinema, the movie had started.
I’m acting as deputy _______ the boss is away.
_______ the rain stopped, we went for a walk.
My mother is cooking _______ my father is preparing for the table.
_______ they ‘turned the TV on TV, the power went out.
Scarcely had he left the office _______ it started raining.
They arrived _______ he was working in the garden.
I was reading the newspaper while you were drying your hair.

Answer keys:

When
while/when
When
while
When
while
When
when
when/while
while

With the complete knowledge of When and While and the practice exercises provided here, PREP believes that you will no longer be confused when encountering these structures in your exams. Make sure to visit PREP regularly to stay updated with the highest quality English language knowledge!

Master Tu Pham

Founder/CEO at Prep

Founder of Prep Smart Test Preparation Platform. With over 10 years of experience in teaching and test preparation, Mr. Tú has helped thousands of students achieve high scores in the IELTS exam. In addition, Mr. Tú Phạm is also a consulting expert in British Council programs and a speaker at many leading educational events, programs, and conferences.