We replace something old with something new.

  • The Mayor has replaced all the old school buses with new ones.

When the sentence is written in the passive voice, "by" is used.

  • All the old school buses have been replaced by new ones.
  • All the old school buses have been replaced by the Mayor.

But what about a sentence in the passive voice that mentions the object that is substituted and the subject who performed the action, the agent? Which preposition should be used?

  • All the old school buses have been replaced by the mayor ....... new ones.
  • 2
    As you suspect, it's with. And you can use either order for the two prepositional phrases; equally good is have been replaced with new ones by the mayor. This is similar to what happens to the ambiguity of the phrase the shooting of the hunters (did the hunters shoot, or were they shot?) when one adds a by-phrase. The shooting of the hunters by the soldiers is quite unambiguous. Aug 20, 2014 at 0:11
  • @JohnLawler Would you answer the question ?
    – Centaurus
    Aug 22, 2014 at 16:32
  • Would you read what I wrote? Aug 22, 2014 at 16:34
  • @JohnLawler I did, but I want to mark the best answer and I don't like the ones I've got so far. Since the question has been seen only 39 times the first two days and chances are very few people will read it from now on, I doubt I will ever mark an answer as the best.
    – Centaurus
    Aug 22, 2014 at 16:40
  • John Lawler has his own reasons for not wanting to play the game. Oct 2, 2014 at 11:29

6 Answers 6


In the examples you are providing, the word "by" refers to the person or object that is performing the action (replacing). Since objects are usually inanimate or incapable of performing actions by themselves, the word "by" would be less likely to be used. The word "with" is used to indicate which objects are the result of the action (replacements).

A good rule to follow when determining which word to use is to attempt to put the sentence in active form. The object or person denoted by the word "by" will always be the noun.

For example:

All the old school buses have been replaced by the mayor with new ones. -> The mayor replaced all the old school buses with new ones.

If you attempted to use the word "by" instead for your blank space, the following transformation would be the result (which is incorrect).

All the old school buses have been replaced by the mayor by new ones. -> The mayor and the new ones replaced all the old school buses.

  • I'm not convinced that's the proper transformation. How about "The mayor replaced all the old school busses by new ones"? (Which is also incorrect!) Aug 21, 2014 at 18:53
  • @PeterShor Which one specifically are you referring to? The nouns or objects specified by the word "by" are always active subjects, verbs or pronouns, if that is the topic to which you are referring. For example, in the sentence "The student got into university by cheating", the verb "cheating" is used as the action word when the sentence is transformed into its active form. The sentence would become: "The student cheated to get into university". Sep 10, 2014 at 20:46

"With" would work better to here in order to avoid the repetition of "by." "All of the old school buses have been replaced by the mayor by new ones" sounds unnecessarily clunky because of that repetition.


A Google Books search for "replaced with new ones by" versus "replaced by new ones by" across books and periodicals published between 1800 and 2008 found 52 unique matches for "replaced with new ones by" and 42 unique matches for "replaced by new ones by." Clearly we're talking about an extremely small pool of examples; but I was somewhat surprised that "replaced by new ones by" did as well as it did. My conclusion is that you can use either preposition before "new ones" in that syntactical setting and not be judged to be badly out of step with the multitude.

Meanwhile, an Ngram chart of "replaced by new ones" (the blue line) versus "replaced with new ones" (the red line) versus "replaced with new ones by" (the green line) and "replaced by new ones by" (the yellow line)—to give a sense of the relatively negligible presence in the Google Books database of the latter two wordings—over the same time period shows a decided preference for "replaced by new ones":

Given that the quoted phrase entails a passive construction, this result appears to be the one you expected. Nevertheless, "replaced with new ones" receives a fairly strong level of support in those instances, particularly in works published in the past century or so. On the strength of these results, I wouldn't go so far as to say that "replaced by new ones" is the only acceptable way to express (in passive voice) the idea of replacing something old by/with something new.


I'm not sure that All the old school busses have been replaced by new ones is correct. In the passive voice "by" shows the person or thing that does the action while "with" shows the thing used to perform the action.

  • 1
    It's the standard passive construction. "New school busses have replaced the old ones", so "the old school busses have been replaced by new ones." The subject of "replace" can be either the agent that does the replacement, or the thing that replaces the old one. Aug 20, 2014 at 0:37

The use of passive voice doesn't necessarily mean that "by" has to be used always in such sentences. "By" has to be used to denote the person who does the action in a passive voice sentence. In the above sentence, the person who does the action is the mayor. The mayor has replaced old buses with new ones. Since the action was not done by new buses, the correct preposition is "with" in this case. For an instance, take a look at the following sentences:

a) The letter was written with a black pen. b) He was stabbed with a sharp knife.

In both of the above sentences, the action was not done by "a black pen", or "a sharp knife", but they were used to carry out the action. Hence, the preposition "by" is incorrect and it should be substituted with "with."

  • You seem to have missed the main point in the question, namely, when we change "New school buses have replaced the old ones" into the passive voice, we use "by", not "with". "The old school buses have been replaced by new ones."
    – Centaurus
    Sep 2, 2014 at 16:50

I think, here 'by' is the better preposition than 'with' because of the word mayor, which is the object. However the preposition 'with' may be more apt without the object, mayor.

Example: The old ones are replaced with new ones.

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