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By and through are both common English prepositions, but they are used in different ways. In many sentences, by shows the method, person responsible for an action, deadline, or means of transport,
while through often describes movement from one side of something to the other, a process, or the means by which something happens.
For example, “I traveled by train” is different from “I walked through the tunnel.”
The difference becomes especially important for English learners because some meanings overlap.
We can say “I learned by practicing” and “I learned through practice,” but the focus changes slightly.
By often emphasizes the method or means, while through can emphasize the process, experience, channel, or intermediary involved. Learning these patterns makes everyday English more natural and precise.
Quick Answer
By usually tells us the method, means, agent, or deadline: “by bus,” “written by Maria,” or “finish by Friday.” Through often describes movement from one side to another, a process, experience, or intermediary: “walk through the door,” “learn through experience,” or “contact us through email.”
Why People Confuse It
People often confuse by vs through because both prepositions can describe how something happens.
Compare:
“She learned English by reading.”
“She learned English through reading.”
Both sentences are possible, but they emphasize slightly different ideas.
By reading focuses on reading as the method she used.
Through reading focuses more on reading as the process or experience through which learning happened.
The two prepositions can also appear in completely different contexts:
- by car → means of transportation
- through the tunnel → movement inside and from one end of a space
- by John → person who performed an action
- through John → an intermediary or channel
- by Friday → no later than Friday
- through Friday → continuing up to and including Friday
Understanding the relationship between the words is more useful than trying to memorize one translation for each preposition.
First Word: By
By is a very flexible preposition. Its meaning changes according to context.
1. By for method or means
Use by to explain how something is done.
“I learned English by watching movies.”
“She improved her writing by practicing every day.”
“You can open the file by clicking this button.”
Here, by + -ing commonly explains the method used to achieve something.
2. By for transportation
Use by with many forms of transportation when describing the general means of travel.
“We traveled by train.”
“He goes to work by bus.”
“They flew by plane.”
But notice the difference:
“I went by bus.”
“I sat on the bus.”
By bus describes the means of transportation, while on the bus describes your position.
3. By for the person who performs an action
In passive sentences, by can identify the agent.
“The novel was written by Jane Austen.”
“The painting was created by a local artist.”
“The decision was made by the committee.”
4. By for deadlines
Use by to mean no later than a particular time.
“Please finish the assignment by Friday.”
This means Friday is the latest acceptable time.
“I will call you by 8 p.m.”
The call will happen at or before 8 p.m.
5. By for measurement or amount
By can also describe measurements or gradual differences.
“The room measures ten feet by twelve feet.”
“Prices increased by 10 percent.”
“We missed the train by five minutes.”
Second Word: Through
Through also has several meanings, but its central ideas often involve movement, a process, experience, or an intermediary.
1. Through for movement inside something
Use through when someone or something moves from one side or part of a space to another.
“We walked through the tunnel.”
“She ran through the door.”
“The train passed through the mountains.”
The idea is movement within or across an enclosed, bounded, or surrounding space.
2. Through for a process
Use through when something happens as a result of a process or experience.
“He learned the skill through experience.”
“She became stronger through hard work.”
“We solved the problem through careful analysis.”
The focus is on the process that led to the result.
3. Through for an intermediary or channel
Use through when something happens with the help of a person, organization, system, or channel.
“I heard about the job through a friend.”
“We booked the hotel through an online agency.”
“She contacted the company through its website.”
The friend, agency, or website acts as a channel or intermediary.
4. Through for a period of time
Through can mean continuing until the end of a stated period.
“The store is open through Sunday.”
This generally means it remains open until and including Sunday.
5. Through for overcoming something
Use through when talking about experiencing or surviving a difficult situation.
“She went through a difficult period.”
“They got through the crisis.”
“He has been through many challenges.”
By vs Through: Comparison Table
| Use | By | Through |
|---|---|---|
| Method | “Learn by practicing.” | “Learn through experience.” |
| Transportation | “Travel by train.” | “Travel through the tunnel.” |
| Agent | “Written by Sarah.” | Not normally used for the direct agent |
| Deadline | “Finish by Friday.” | “Work through Friday.” |
| Movement | Less common for movement inside a space | “Walk through the door.” |
| Process | “Improve by practicing.” | “Improve through practice.” |
| Intermediary | Usually not used this way | “I found it through a friend.” |
| Duration | “By Monday” = no later than Monday | “Through Monday” = continuing until Monday |
| Measurement | “Ten by twelve feet.” | Not normally used |
| Cause/means | “By using this method…” | “Through careful planning…” |
When to Use Each
Use “by” when you mean “using this method”
“She learned by practicing.”
Think:
How did she learn? → By practicing.
Use “through” when you mean “as a result of or during this process”
“She learned through experience.”
Think:
What process or experience led to the learning? → Through experience.
Use “by” for a deadline
“Submit the form by Monday.”
This means Monday is the latest time.
Use “through” for continuation
“The office is closed through Monday.”
This means the closure continues until and including Monday.
Use “by” for transportation
“We traveled by train.”
Use “through” for movement inside a place
“We traveled through the tunnel.”
These two can appear in the same sentence:
“We traveled by train through the tunnel.”
Here, by train tells us the means of transportation, while through the tunnel tells us the route.
10+ Examples of By vs Through
1. Learning
“You can improve your vocabulary by reading.”
“You can improve your vocabulary through regular reading.”
By emphasizes the method; through emphasizes the process.
2. Transportation
“We went by train.”
“The train went through the tunnel.”
By = means of transportation.
Through = movement within a space.
3. Communication
“I contacted her by phone.”
“I contacted her through her assistant.”
By phone describes the communication method.
Through her assistant identifies an intermediary.
4. Learning from experience
“He learned by making mistakes.”
“He learned through experience.”
Both are natural, but the emphasis differs slightly.
5. Deadline
“Please arrive by 9 a.m.”
You should arrive no later than 9 a.m.
“The event runs through Friday.”
The event continues until and including Friday.
6. Passive voice
“The book was written by a famous author.”
By identifies who performed the action.
7. A channel
“I found the apartment through a friend.”
The friend was the connection or channel.
8. Movement
“The children ran through the garden.”
The children moved within the garden and across it.
9. Method
“She solved the problem by using a calculator.”
The calculator was part of the method.
10. Process
“The company grew through careful planning.”
Careful planning was the process or means through which growth occurred.
11. Experience
“He gained confidence through practice.”
Practice was the experience or process that produced the result.
12. Passing from one side to another
“Light came through the window.”
The light passed through the window.
Common Mistakes
Mistake 1: Using “through” for every method
Not every method requires through.
❌ “I traveled through bus.”
✅ “I traveled by bus.”
Use by for the general means of transportation.
Mistake 2: Confusing “by Friday” and “through Friday”
These have different meanings.
by Friday = no later than Friday
through Friday = continuing until and including Friday
Compare:
“Send the application by Friday.”
The deadline is Friday.
“The exhibition runs through Friday.”
The exhibition continues until Friday.
Mistake 3: Using “by” for movement inside a space
❌ “We walked by the tunnel.”
This normally means you walked past or beside the tunnel.
✅ “We walked through the tunnel.”
This means you entered it and moved inside it.
Mistake 4: Confusing “by” with “through” after communication words
Both can sometimes be correct, but the meaning may change.
“I contacted him by email.”
Email is the method.
“I contacted him through his assistant.”
The assistant was the intermediary.
Mistake 5: Forgetting “by + -ing”
When by explains a method, it is commonly followed by a gerund.
“She improved by practicing.”
Not:
❌ “She improved by practice English.”
Memory Trick
Remember:
BY = HOW?
“How did you do it?”
“By practicing.”
THROUGH = WHAT PROCESS, EXPERIENCE, CHANNEL, OR SPACE?
“Through experience.”
“Through a friend.”
“Through the tunnel.”
A short memory formula is:
By = method or agent
Through = process, passage, or intermediary
American vs British English
By and through have essentially the same meanings in American and British English.
Both varieties commonly use:
“travel by train”
“walk through the park”
“finish by Friday”
“open through Sunday”
There can be regional differences in preferred expressions or interpretation of particular time phrases, but the basic distinction between by and through remains the same.
One useful point for learners is that through is often used more explicitly when talking about continuation:
“The shop is open through Friday.”
In both American and British English, this generally indicates that Friday is included.
Similar Words
Via
Via means using a route, person, place, or method.
“We flew to London via Dubai.”
“I sent the documents via email.”
Via is often close to through when describing a route or channel.
With
With often describes the tool or instrument used to do something.
“She cut the paper with scissors.”
Compare:
“She improved by practicing.”
By describes the method; with describes the instrument.
During
During refers to a period when something happens.
“I fell asleep during the movie.”
It does not usually express the same idea as through.
Across
Across means from one side to another.
“We walked across the bridge.”
Compare:
“We walked through the tunnel.”
Along
Along means following the length or direction of something.
“We walked along the river.”
Past
Past means moving beyond or beside something.
“We walked past the school.”
Compare:
“We walked through the school.”
The first means you went beside or beyond it; the second suggests movement inside it.
Final Verdict
The easiest way to distinguish by vs through is to ask what relationship you want to express.
Use by for a method, means, agent, deadline, or measurement:
“by train”
“by practicing”
“written by Maria”
“by Friday”
Use through for movement across or inside a space, a process, experience, an intermediary, or continuation through a period:
“through the tunnel”
“through experience”
“through a friend”
“through Friday”
When both seem possible, ask yourself whether you are emphasizing the method used or the process, channel, experience, or route involved.
FAQs
1. What is the main difference between by and through?
By commonly expresses a method, means, agent, or deadline. Through commonly expresses movement within or across a space, a process, experience, an intermediary, or continuation over a period.
2. Is it “by bus” or “through bus”?
The correct expression is by bus when you mean the means of transportation.
“I traveled by bus.”
You can use through with a route:
“The bus went through the tunnel.”
3. What is the difference between “by Friday” and “through Friday”?
By Friday means no later than Friday.
Through Friday means something continues until and including Friday.
“Finish it by Friday.”
“The office is closed through Friday.”
4. Should I say “by email” or “through email”?
By email is very common when describing email as the communication method.
“Please send the document by email.”
Through email can also be used when emphasizing email as a channel, but by email is generally the more straightforward choice for the method of communication.
5. What is the difference between “by practicing” and “through practice”?
By practicing emphasizes practice as the method used to achieve a result.
Through practice emphasizes practice as the process or experience that produces the result.
Both can be grammatically correct.
6. Is “through” the same as “via”?
They can overlap when describing a route or channel.
“We traveled through Dubai.”
“We traveled via Dubai.”
However, through has additional meanings involving movement within a space and processes, while via is more specifically associated with a route or means.
7. Is “by” used for passive voice?
Yes. By can identify the person or thing responsible for an action in a passive sentence.
“The novel was written by George Orwell.”
8. What preposition should I use for movement inside a place?
Use through when you mean movement inside or from one side of a space to another.
“She walked through the door.”
“They drove through the tunnel.”
Remember This
BY often answers:
How? By what method? By whom? By when?
THROUGH often answers:
Through what space? Through what process? Through whom? Until when?
The most useful examples are:
- by bus = means of transportation
- through the tunnel = movement inside a space
- by practicing = method
- through experience = process
- written by her = agent
- through a friend = intermediary
- by Friday = deadline
- through Friday = continuing until Friday
Conclusion
By and through are both important English prepositions, but they usually emphasize different relationships. By commonly focuses on the method, means, person responsible for an action, or deadline. Through commonly focuses on movement, a process, an experience, a channel, or continuation over time.
When choosing between them, do not translate the prepositions word for word. Instead, look at the meaning of the entire sentence. Ask whether you mean how something happens or whether you mean the route, process, experience, intermediary, or period through which something happens. That simple distinction will help you use by and through naturally and accurately.
