According to the dictionary definition, the word "replace" can mean: "put something newer or in better condition in place of something old or in poor condition.

Almost no dictionary has mentioned that the verb "substitute" can be used in this sense too; but sometimes I have heard some people (perhaps non-natives) used it instead of "replace" in this sense.

I was wondering if we can use them interchangeably this this sense or not? Please kindly clarify it.

For more explanations, I have made an example. Please consider it and let me know if they can be used interchangeably or not:

I'm sorry Simon! I know that you loved the vase I broke, but:

1- I promise to replace it.
2- I promise to substitute it.

Connotation: I promise to buy an exactly the same vase and put it instead of your broken vase

Please kindly enlighten me.

  • 1
    Your second version (I promise to substitute it) is syntactically valid, but idiomatically uncommon. To compare like with like, consider I promise to get you a replacement / substitute. To most native speakers, using replacement in that context would more strongly imply exact replacement, replica, whereas a substitute is more likely to mean a very similar replacement (not an exact copy), that it's hoped will functionally and/or aesthetically acceptable. Sep 18, 2019 at 13:00
  • The related ELU question “Replace with” versus “replace by” contains potentially relevant information regarding the by/with preposition choice (but note that whereas we can also say He substituted X for Y, we never say He replaced X for Y). Sep 18, 2019 at 13:34

2 Answers 2


The difference between substitute and replace / replacement is subtle and differs in various contexts.

A substitute (as a noun) usually infers that the replacement item is not exactly the same as the original. It doesn't necessarily mean inferior, just different. For example:

Potassium chloride is a salt substitute.

This example means that potassium chloride can be is used in place of salt. It doesn't mean it is better or worse, nor does it mean that it supplants or replaces it permanently.

Substitute often means that the replacement is temporary - for example, a substitute teacher is one that teaches while your usual teacher is unavailable. By contrast a replacement teacher would suggest your old teacher has been permanently replaced.

However, substitute as a verb can mean that the exchange is permanent, for example:

He substituted the broken vase with another.

As the original is broken, it may never return.

The main difference between the verbs "replace" and "substitute" is that substitute implies that the new item is different in some way, while replace would normally suggest that the new item of the same kind or type, for example:

My son dropped his ice-cream so I replaced it.

This would suggest that you bought him another ice-cream.

  • Thank you @Astralbee. I have received the answer to the original question, but some other questions have been formed in my mind! Ex1: Based on the current technologies, there isn’t any better (substitute / replacement) for airplane, but there are multiple alternatives like bus, train, etc. Connotation: "nothing can take the place airplane; at least for now." Ex2 There is no (substitute / replacement) for hard work. Connotation: "nothing can take the place of hard work forever." To me, in both examples, "replacement" is the correct choice. Do you confirm?
    – A-friend
    Sep 19, 2019 at 8:38
  • @A-friend some of the uses are idiomatic and not necessarily explainable in the form of a dictionary definition. That said, a "replacement bus" is idiomatic, and as it is intended to provide the same service, seems apt. There are lots of buses and trains and so a like-for-like replacement is possible. That isn't the case with "there is no substitute for hard work". Anything other than hard work would be a "substitute", because it is not the same or comparable thing.
    – Astralbee
    Sep 19, 2019 at 10:33
  • I see @Astralbee. Thinking twice, I think based on a context, each word would be possible. Thank you very much.
    – A-friend
    Sep 19, 2019 at 10:41
  • Also, @Astralbee you have written: "By contrast a replacement teacher would suggest...!" "Replacement" is a noun and no dictionary has defined it as an adjective! I am wondering if it is an attributive adjective.
    – A-friend
    Sep 19, 2019 at 12:45
  • @A-friend I haven't said that either of them are adjectives. They both have noun and verb forms. The verb is to replace.
    – Astralbee
    Sep 20, 2019 at 8:17

One important distinction between replace and substitute is that they have different referents: in the situation where A's place is taken by B, A is replaced and B is substituted. So the following expression is incorrect:

He substituted the broken vase with another.

It should instead be either

He replaced the broken vase with another.


He substituted another vase for the broken one.

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