Replace With vs. Replace By – Which is Correct?

While both phrases can be encountered, “replace with” is overwhelmingly the correct and standard usage when indicating the substitute item. “Replace by” is grammatically permissible, particularly in passive voice constructions to specify the agent performing the replacement, but it is much less common and often sounds awkward when “with” is the intended meaning. Use “replace with” when substituting one item for another.

Replace With or Replace By – Which is Correct?

The choice between “replace with” and “replace by” hinges on a subtle but significant distinction in meaning, specifically regarding what element of the action you are emphasizing. In most contexts where you are indicating what new item is taking the place of an old one, “replace with” is the correct and natural phrase to use. It clearly states the substitute.

“Replace by,” on the other hand, is far less common and typically appears in passive voice constructions to identify the agent or force responsible for the replacement. It signifies who or what performed the action, rather than what new item was introduced. For instance, you might say, “The old system was replaced by a team of engineers,” referring to the agent, but “The old system was replaced with a new one,” referring to the substitute.

The Best Trick to Remember the Difference

To easily remember when to use each phrase, consider the primary focus of your sentence:

• If you are specifying the new item or person being introduced as a substitute, think of it as “what you are replacing it with.” This almost always means using “replace with.”
• If you are specifying the agent or cause that performed the act of replacing (typically in a passive sentence), think of it as “who or what it was replaced by.” This is where “replace by” might apply, though “by” can often be omitted or rephrased for better clarity.

A simple “swap test” can also help: If you can rephrase the sentence to “substitute X for Y,” then “replace X with Y” is almost certainly correct.

Word/Phrase	Part of Speech	Meaning	Example
Replace with	Phrasal verb / Idiomatic expression	To substitute one thing for another; to put something new in the place of something old.	We need to replace the broken chair with a new one.
Replace by	Phrasal verb (less common)	To be substituted by an agent or cause (usually in passive voice).	The old traditions were gradually replaced by modern customs.

How to Use Replace With

“Replace with” is the standard idiomatic expression used when you are removing one item, person, or concept and putting another in its place. The preposition “with” introduces the new item that is being used as the substitute. This phrase is versatile and can be used in both formal and casual contexts, making it the go-to choice for almost all substitution scenarios. It implies a direct exchange or substitution.

Example 1: The company decided to replace all old computers with newer, more efficient models.

Example 2: Can you replace the empty milk carton with a full one from the fridge?

Example 3: After the scandal, the CEO was replaced with a more ethical leader.

What are the different forms of Replace With?

The phrase “replace with” is made up of the verb “replace” and the preposition “with.” Only the verb “replace” changes its form to reflect tense, mood, or voice. The preposition “with” remains constant.

• Base Form: replace with (e.g., We need to replace with…)
• Present Simple (3rd person singular): replaces with (e.g., He replaces with…)
• Present Participle: replacing with (e.g., They are replacing with…)
• Past Simple: replaced with (e.g., She replaced with…)
• Past Participle: replaced with (e.g., It has been replaced with…)

For example, in a sentence: “The broken window was replaced with a new pane of glass.” (passive voice, past participle)

Etymology of the word Replace With

The verb “replace” comes from the Old French “replacer,” meaning “to place again,” which itself is derived from “re-” (again) and “placer” (to place). Its usage in English dates back to the late 16th century. The preposition “with” has Old English roots (“wið”), originally meaning “against, opposite, toward,” but evolving to denote accompaniment, instrument, or, in this case, substitution, by the Middle English period. The combination “replace with” became established as the standard idiom for substitution, indicating the item being used to fill the void.

How to Use Replace By

“Replace by” is used in more specific circumstances, almost exclusively in passive voice constructions, to denote the agent or cause of the replacement. It answers the question “by whom?” or “by what?” was the action of replacing carried out. While grammatically correct in these specific passive contexts, it is significantly less common than “replace with” and can sometimes sound formal or slightly awkward if “with” is the intended meaning of substitution.

Example 1: The old traditional methods were gradually replaced by more modern, efficient techniques.

Example 2: In the play, the lead actor was suddenly replaced by his understudy due to illness.

Example 3: The damaged bridge will be replaced by a new structure designed to withstand stronger currents.

What are the different forms of Replace By?

Similar to “replace with,” only the verb “replace” conjugates for tense, mood, and voice when used in the phrase “replace by.” The preposition “by” remains unchanged.

• Base Form: replace by (e.g., It will be replaced by…)
• Present Simple (3rd person singular): replaces by (less common in passive agent context)
• Present Participle: replacing by (e.g., being replaced by…)
• Past Simple: replaced by (e.g., It was replaced by…)
• Past Participle: replaced by (e.g., It has been replaced by…)

For example, in a sentence: “The outdated software is being replaced by a new open-source solution.” (passive voice, present continuous)

Etymology of the word Replace By

The etymology of “replace” is the same as discussed previously, stemming from Old French “replacer.” The preposition “by” traces its origins to Old English “bī,” meaning “near, beside, by, during.” Over time, “by” developed various senses, including indicating the agent in a passive construction (e.g., “written by Shakespeare”). When combined with “replace,” “by” serves this specific agentive function, identifying the force or party responsible for the act of substitution, rather than the substitute itself.

Related Concepts

Understanding these broader grammatical concepts can help clarify the appropriate use of “replace with” and “replace by.”

• Phrasal Verbs and Prepositional Phrases: Many verbs combine with prepositions to create idiomatic expressions whose meaning cannot be fully deduced from the individual words. “Replace with” functions as a common prepositional phrase, where “with” specifically indicates the item used for substitution. The precise choice of preposition is crucial for conveying the intended meaning.
• Active vs. Passive Voice: The distinction between “replace with” and “replace by” is often tied to sentence voice. “Replace with” is used in both active (“We replaced X with Y”) and passive (“X was replaced with Y”) voice to introduce the substitute. “Replace by,” however, is almost exclusively used in the passive voice (“X was replaced by Y”) to introduce the agent performing the action, not the substitute itself.

Examples from Media and Literature

• “The old guard must be replaced with fresh faces and new ideas.” (News commentary)
• “He decided to replace the missing pages with photocopies from another edition.” (Literary context)
• “In many industries, manual labor has been replaced by automation and robotics.” (Scientific journal)
• “The traditional paper ballot system was replaced with electronic voting machines.” (Government report)
• “The original score was replaced by a contemporary soundtrack for the film’s re-release.” (Film review)

Practice Exercises

Choose the correct word or phrase to complete the sentence.

1. The broken light bulb needs to be replaced _______ a new one.
2. The ancient forest was gradually replaced _______ a sprawling urban development.
3. The chef decided to replace butter _______ olive oil in the recipe for a healthier option.
4. After the scandal, the director was replaced _______ an interim manager.
5. Many manual tasks are now being replaced _______ artificial intelligence.

Answer Key

1. with
2. by
3. with
4. with
5. by

Replace With Synonyms

Synonym	Definition
Substitute	Use or act in place of another.
Exchange	Give something and receive something else in return.
Supplant	Supersede and replace.
Swap	Give one thing in exchange for another.
Interchange	Put each of two things in the place of the other.

Replace By Synonyms

While “replace by” focuses on the agent, the synonyms for the core action of “replace” are largely the same. However, when considering the agentive aspect, related concepts might include:

Synonym / Related Concept	Definition / Explanation
Supplant (by)	To take the place of (another), especially through force, cleverness, or the gradual erosion of influence. (e.g., monarchs supplanted by republics)
Displace (by)	To take over the place, position, or role of (someone or something). (e.g., workers displaced by machines)
Oust (by)	Drive out or expel (someone) from a position or place. (e.g., a leader ousted by popular vote)
Supercede (by)	Take the place of (a person or thing previously in authority or use); supplant. (e.g., old laws superceded by new legislation)

Frequently Asked Questions

Question 1: Is “replaced by” always incorrect?
No, “replaced by” is not always incorrect. It is grammatically acceptable and appropriate when you want to specify the agent or cause that performed the act of replacing, typically in a passive sentence. However, it is far less common than “replace with” and should be used cautiously to avoid awkward phrasing if you simply mean to introduce a substitute.

Question 2: Can I use “replaced with” in a passive sentence?
Yes, absolutely. “Replaced with” can be used in both active and passive voice to introduce the item that serves as the substitute. For example, “The old car was replaced with a new model.” Here, “with a new model” indicates the substitute, not the agent.

Question 3: Which phrase is more common in everyday English?
“Replace with” is significantly more common and natural in everyday English. It is the default phrase for expressing substitution. “Replace by” is much rarer and tends to be reserved for specific contexts where the agent of replacement needs to be highlighted.

Conclusion

Navigating the nuances of “replace with” and “replace by” comes down to understanding the role each preposition plays. While “replace with” is the universally accepted and most common choice for introducing a substitute item, “replace by” serves a distinct, albeit less frequent, purpose in identifying the agent or cause of replacement, primarily in passive constructions. By focusing on whether you are naming the substitute or the performer of the action, you can confidently choose the correct phrase.

Pro Tip: When in doubt, “replace with” is almost always the safer and more idiomatic choice for clear communication about substitution. Using “replace by” incorrectly can make your writing sound unnatural or ambiguous, potentially undermining your professional credibility.