Understanding Prepositions of Agent: A Comprehensive Guide

Prepositions of agent are essential for indicating who or what performs an action in a sentence, particularly in passive voice constructions. Mastering these prepositions enhances your ability to express agency clearly and accurately, making your writing and speech more precise and sophisticated. This guide provides a comprehensive overview of prepositions of agent, including definitions, examples, usage rules, and practice exercises. It is designed for English language learners of all levels who wish to improve their understanding and use of these important grammatical tools.

Whether you’re a beginner aiming to grasp the basics or an advanced learner seeking to refine your skills, this article offers valuable insights and practical exercises to solidify your knowledge. By understanding the nuances of prepositions of agent, you can avoid common errors and communicate more effectively in a variety of contexts.

Table of Contents

1. Introduction
2. Definition of Preposition of Agent
3. Structural Breakdown
4. Types and Categories
5. Examples of Prepositions of Agent
6. Usage Rules
7. Common Mistakes
8. Practice Exercises
9. Advanced Topics
10. FAQ
11. Conclusion

Definition of Preposition of Agent

A preposition of agent is a preposition that introduces the agent performing an action, typically in a passive voice sentence. The agent is the person or thing responsible for the action described by the verb. These prepositions connect the action to its performer, providing clarity and context to the sentence. The most common prepositions of agent are “by” and occasionally “with,” although “with” indicates the instrument used rather than the agent in some cases.

In active voice, the agent is the subject of the sentence and performs the action directly. However, when the sentence is transformed into passive voice, the object of the active sentence becomes the subject, and the agent is introduced by a preposition. Understanding this transformation is crucial for identifying and using prepositions of agent correctly. The use of prepositions of agent allows for a shift in focus, emphasizing the action rather than the actor, or when the actor is unknown or unimportant.

Classification

Prepositions of agent primarily fall under the broader category of prepositions of relationship. They establish a relationship between the action and the entity performing it. While “by” is the most frequent and versatile preposition of agent, “with” can also function as one, especially when referring to instruments or tools used to perform an action. However, it’s essential to distinguish between “with” indicating agency and “with” indicating accompaniment or possession. Further examples might include less common uses of prepositions like “through” in specific contexts, though these are rarer and often carry slightly different connotations.

Function

The primary function of a preposition of agent is to identify the entity responsible for an action described by a verb in the passive voice. This is particularly important when the agent is not immediately obvious or when the speaker or writer wants to emphasize the action rather than the actor. Without the preposition of agent, the sentence might lack crucial information about who or what caused the action to occur. It adds specificity and clarity to the sentence, preventing ambiguity and ensuring accurate communication.

Contexts

Prepositions of agent are commonly used in various contexts, including:

• Scientific writing: Describing experiments and procedures, where the agent performing the action is often a tool or instrument.
• Legal documents: Assigning responsibility for actions or outcomes.
• News reports: Reporting events and identifying the individuals or entities involved.
• Literary works: Creating narrative voice and perspective.
• Everyday conversations: Describing actions and their performers in a variety of situations.

Structural Breakdown

The structure involving prepositions of agent is typically found in passive voice sentences. The basic pattern is: Subject (receiver of the action) + Verb (passive form) + Preposition of Agent + Agent (performer of the action). The passive form of the verb usually consists of a form of “to be” (is, are, was, were, been) + past participle of the main verb.

Understanding how to transform active voice sentences into passive voice sentences is essential for using prepositions of agent correctly. In active voice, the subject performs the action. In passive voice, the subject receives the action, and the original subject (agent) is introduced by the preposition of agent. For example, the active sentence “The dog chased the cat” becomes “The cat was chased by the dog” in passive voice.

Let’s break down the structure with examples:

1. Subject (Receiver of Action): The letter
2. Verb (Passive Form): was written
3. Preposition of Agent: by
4. Agent (Performer of Action): John
5. Complete Sentence: The letter was written by John.

Another example:

1. Subject (Receiver of Action): The cake
2. Verb (Passive Form): was decorated
3. Preposition of Agent: with
4. Agent (Performer of Action – Instrument): frosting
5. Complete Sentence: The cake was decorated with frosting.

Types and Categories

While “by” is the most common preposition of agent, “with” can also be used to indicate the instrument or tool used to perform an action. It’s important to differentiate between these two types of prepositions to ensure accuracy in your writing and speech.

“By” as a Preposition of Agent

The preposition “by” is used to indicate the person or entity that performs the action. It is the most straightforward and widely used preposition of agent. It clearly identifies who or what is responsible for the action described in the passive voice sentence.

For example:

• The book was written by J.K. Rowling.
• The house was built by the construction crew.
• The song was sung by the choir.

“With” Indicating Instrument

The preposition “with” is used to indicate the instrument or tool used to perform the action. While it doesn’t identify the actual agent (the person), it specifies the means by which the action was carried out. This is common when describing how something was done, rather than who did it.

For example:

• The door was opened with a key.
• The painting was created with oil paints.
• The bread was sliced with a knife.

Distinguishing “By” and “With”

It’s crucial to distinguish between “by” and “with” to ensure you’re accurately conveying the agent or instrument involved in the action. “By” identifies the actor, while “with” identifies the tool or means. Misusing these prepositions can lead to confusion and misinterpretation.

Consider these examples:

• Incorrect: The door was opened by a key.
• Correct: The door was opened with a key.
• Incorrect: The painting was created with the artist.
• Correct: The painting was created by the artist.

Here’s a table summarizing the differences:

Preposition	Indicates	Example
By	The agent (person or entity performing the action)	The report was written by the committee.
With	The instrument or tool used to perform the action	The cake was decorated with frosting.

Examples of Prepositions of Agent

The following tables provide extensive examples of sentences using prepositions of agent, categorized by the preposition used (“by” or “with”) and the context in which they are used. These examples will help you understand the correct usage of these prepositions in various situations.

Examples with “By”

The following table showcases sentences using “by” as the preposition of agent. Notice how “by” always introduces the person, group, or entity responsible for the action.

Sentence	Explanation
The novel was written by a famous author.	Indicates the author who wrote the novel.
The project was completed by the team.	Specifies the team responsible for completing the project.
The law was passed by the parliament.	Identifies the parliament as the entity that passed the law.
The meal was prepared by the chef.	Indicates the chef who prepared the meal.
The car was driven by the experienced driver.	Specifies the driver who drove the car.
The email was sent by the marketing department.	Identifies the department that sent the email.
The mistake was made by the intern.	Indicates the intern who made the mistake.
The presentation was given by the CEO.	Specifies the CEO who gave the presentation.
The decision was made by the board of directors.	Identifies the board as the entity that made the decision.
The experiment was conducted by the scientists.	Indicates the scientists who conducted the experiment.
The website was designed by the web developer.	Specifies the web developer who designed the website.
The building was constructed by the construction company.	Identifies the company that constructed the building.
The song was composed by the musician.	Indicates the musician who composed the song.
The play was directed by the theater director.	Specifies the director who directed the play.
The sculpture was created by the artist.	Identifies the artist who created the sculpture.
The film was produced by the production company.	Indicates the company that produced the film.
The article was written by the journalist.	Specifies the journalist who wrote the article.
The recipe was created by the food blogger.	Identifies the food blogger who created the recipe.
The application was developed by the software engineer.	Indicates the software engineer who developed the application.
The event was organized by the event planner.	Specifies the event planner who organized the event.
The game was won by our team.	Identifies our team as the winner.
The report was reviewed by the manager.	Specifies the manager who reviewed the report.
The error was corrected by the editor.	Identifies the editor who corrected the error.
The package was delivered by the courier.	Specifies the courier who delivered the package.
The presentation was well-received by the audience.	Identifies the audience as the receiver of the presentation.
The problem was solved by the engineer.	Specifies the engineer who solved the problem.
The contract was signed by both parties.	Identifies both parties as the signers of the contract.

Examples with “With”

The following table showcases sentences using “with” to indicate the instrument or tool used to perform an action. Note that “with” specifies the means, not the agent.

Sentence	Explanation
The door was opened with a key.	Indicates that a key was used to open the door.
The painting was created with oil paints.	Specifies that oil paints were used to create the painting.
The bread was sliced with a knife.	Indicates that a knife was used to slice the bread.
The cake was decorated with frosting.	Specifies that frosting was used to decorate the cake.
The letter was sealed with wax.	Indicates that wax was used to seal the letter.
The hole was dug with a shovel.	Specifies that a shovel was used to dig the hole.
The wood was cut with a saw.	Indicates that a saw was used to cut the wood.
The car was cleaned with soap and water.	Specifies that soap and water were used to clean the car.
The floor was polished with wax.	Indicates that wax was used to polish the floor.
The wound was treated with antiseptic.	Specifies that antiseptic was used to treat the wound.
The picture was taken with a camera.	Indicates that a camera was used to take the picture.
The document was signed with a pen.	Specifies that a pen was used to sign the document.
The soup was stirred with a spoon.	Indicates that a spoon was used to stir the soup.
The garden was watered with a hose.	Specifies that a hose was used to water the garden.
The furniture was dusted with a cloth.	Indicates that a cloth was used to dust the furniture.
The meal was eaten with chopsticks.	Specifies that chopsticks were used to eat the meal.
The knot was tied with rope.	Indicates that rope was used to tie the knot.
The message was sent with a phone.	Specifies that a phone was used to send the message.
The problem was solved with logic.	Indicates that logic was used to solve the problem.
The code was written with Python.	Specifies that Python was used to write the code.
The building was secured with locks.	Indicates that locks were used to secure the building.
The table was set with silverware.	Specifies that silverware was used to set the table.
The information was gathered with research.	Indicates that research was used to gather the information.
The project was managed with software.	Specifies that software was used to manage the project.
The task was completed with effort.	Indicates that effort was used to complete the task.
The design was created with software.	Specifies that software was used to create the design.

Combined Examples

This table provides examples that help distinguish between using “by” and “with” in similar contexts, highlighting the difference between the agent and the instrument.

Sentence with “By”	Sentence with “With”	Explanation
The cake was baked by Mary.	The cake was decorated with frosting.	“By Mary” indicates who baked the cake; “with frosting” indicates what was used to decorate it.
The door was opened by the security guard.	The door was opened with a key.	“By the security guard” indicates who opened the door; “with a key” indicates what was used to open it.
The letter was written by John.	The letter was written with a pen.	“By John” indicates who wrote the letter; “with a pen” indicates what was used to write it.
The picture was taken by the photographer.	The picture was taken with a camera.	“By the photographer” indicates who took the picture; “with a camera” indicates what was used to take it.
The house was built by the construction crew.	The house was built with bricks and mortar.	“By the construction crew” indicates who built the house; “with bricks and mortar” indicates what materials were used.
The report was written by the analyst.	The report was analyzed with specialized software.	“By the analyst” indicates who wrote the report; “with specialized software” indicates what tool was used for analysis.
The problem was solved by the engineer.	The problem was solved with a mathematical equation.	“By the engineer” indicates who solved the problem; “with a mathematical equation” indicates the method used.
The code was written by the programmer.	The code was written with Python.	“By the programmer” indicates who wrote the code; “with Python” indicates the language used.
The meal was prepared by the chef.	The meal was cooked with fresh ingredients.	“By the chef” indicates who prepared the meal; “with fresh ingredients” indicates what was used in the preparation.

Usage Rules

Using prepositions of agent correctly involves understanding when and how to use “by” and “with.” Here are the key rules to follow:

1. Use “by” to indicate the person or entity performing the action. This is the most common usage and applies to all situations where you want to identify the agent.
2. Use “with” to indicate the instrument or tool used to perform the action. This is used when you want to specify the means by which the action was carried out.
3. Ensure the sentence is in passive voice when using prepositions of agent. The subject of the sentence should be the receiver of the action, not the performer.
4. Avoid using prepositions of agent in active voice sentences. Active voice sentences already clearly identify the agent as the subject.
5. Be mindful of the context to choose the appropriate preposition. Consider whether you want to identify the actor or the tool used.

Exceptions and Special Cases

While the rules above are generally applicable, there are a few exceptions and special cases to consider:

• When the agent is unknown or unimportant, the prepositional phrase can be omitted. For example, “The window was broken” (agent unknown).
• In some cases, other prepositions might be used to indicate agency, but these are rare and often carry different connotations. For example, “The city was destroyed through negligence” (though “through” here indicates cause more than direct agency).

Common Mistakes

One of the most common mistakes is confusing “by” and “with.” Here are some examples of common errors and how to correct them:

Incorrect	Correct	Explanation
The door was opened by a key.	The door was opened with a key.	“By” should be used for the agent, not the instrument.
The painting was created with the artist.	The painting was created by the artist.	“With” should be used for the instrument, not the agent.
The report was written with the committee.	The report was written by the committee.	“With” should be used for the instrument, not the agent.
The cake was baked with John.	The cake was baked by John.	“With” indicates you baked alongside John, not that he was the agent.

Another common mistake is using prepositions of agent in active voice sentences. This is unnecessary and grammatically incorrect. For example:

• Incorrect: John wrote the letter by himself.
• Correct: John wrote the letter.

Practice Exercises

Test your understanding of prepositions of agent with these practice exercises. Choose the correct preposition (“by” or “with”) to complete each sentence.

Exercise 1: Choose the Correct Preposition

Question	Answer
The book was written ______ a famous author.	by
The door was locked ______ a key.	with
The cake was decorated ______ sprinkles.	with
The song was sung ______ the choir.	by
The picture was painted ______ Van Gogh.	by
The window was cleaned ______ a cloth.	with
The meal was prepared ______ the chef.	by
The letter was sent ______ mail.	by
The wood was cut ______ an axe.	with
The mistake was made ______ me.	by

Exercise 2: Rewrite Active Sentences in Passive Voice

Rewrite the following active sentences in passive voice, using the appropriate preposition of agent.

Active Sentence	Passive Sentence
The dog chased the cat.	The cat was chased by the dog.
The chef prepared the meal.	The meal was prepared by the chef.
The artist painted the picture.	The picture was painted by the artist.
The construction crew built the house.	The house was built by the construction crew.
The gardener watered the plants.	The plants were watered by the gardener.
The wind blew down the tree.	The tree was blown down by the wind.
The student answered the question.	The question was answered by the student.
The mechanic fixed the car.	The car was fixed by the mechanic.
The teacher graded the papers.	The papers were graded by the teacher.
The author wrote the book.	The book was written by the author.

Exercise 3: Fill in the Blanks

Complete the following sentences using “by” or “with” and the appropriate word from the list provided. (Words: hammer, architect, programmer, knife, committee)

Sentence	Answer
The nail was driven ______ a ______.	with, hammer
The building was designed ______ the ______.	by, architect
The code was written ______ the ______.	by, programmer
The bread was cut ______ a ______.	with, knife
The decision was made ______ the ______.	by, committee

Advanced Topics

For advanced learners, understanding the nuances of prepositions of agent in more complex sentence structures and idiomatic expressions is crucial. This includes recognizing when the agent is implied but not explicitly stated, and understanding how prepositions of agent interact with other grammatical elements.

One advanced topic is the use of the passive voice to avoid assigning blame or responsibility. In such cases, the prepositional phrase indicating the agent is often omitted to maintain neutrality or avoid conflict. For example, “Mistakes were made” (agent unspecified).

Another advanced topic is the use of prepositions of agent in complex sentences with multiple clauses. In these cases, it’s important to ensure that the prepositional phrase is clearly connected to the correct verb and subject. For example, “The report, which was written by John, was reviewed by the manager.”

FAQ

Here are some frequently asked questions about prepositions of agent:

1. What is the difference between active and passive voice?

   In active voice, the subject performs the action (e.g., “John wrote the letter”). In passive voice, the subject receives the action, and the agent is introduced by a preposition (e.g., “The letter was written by John”).

2. When should I use the passive voice?

   Use the passive voice when you want to emphasize the action rather than the actor, when the actor is unknown or unimportant, or when you want to avoid assigning blame or responsibility.

3. Can I omit the prepositional phrase indicating the agent?

   Yes, you can omit the prepositional phrase when the agent is unknown, unimportant, or obvious from the context.

4. Is it always necessary to include the agent in a passive voice sentence?

   No, it is not always necessary. If the agent is unknown or irrelevant, it can be omitted. For example, “The window was broken.”

5. How can I avoid confusing “by” and “with”?

   “By” indicates the agent (the person or entity performing the action), while “with” indicates the instrument or tool used to perform the action. Always consider whether you want to identify the actor or the means.

6. Are there any other prepositions that can be used as prepositions of agent?

   While “by” and “with” are the most common, other prepositions like “through” might be used in specific contexts, but these are rare and often carry slightly different connotations.

7. What if I want to emphasize both the actor and the instrument?

   You can use both “by” and “with” in the same sentence. For example, “The door was opened by the security guard with a key.”

8. Is the passive voice weaker than the active voice?

   The passive voice is not inherently weaker, but it can sometimes make writing sound less direct or less engaging. Use it strategically to achieve your desired effect.

Conclusion

Understanding and correctly using prepositions of agent is crucial for clear and effective communication in English. By mastering the rules and nuances of “by” and “with,” you can enhance your ability to express agency accurately in passive voice constructions. Remember to distinguish between the agent (who performs the action) and the instrument (what is used to perform the action), and practice identifying and correcting common mistakes.

Continue to practice using prepositions of agent in your writing and speech, and pay attention to how they are used in the texts you read and the conversations you hear. With consistent effort, you will develop a strong command of these important grammatical tools and improve your overall English proficiency. Remember, language learning is a continuous journey, and every step you take brings you closer to fluency.