Consider the following self-made sentences:

  1. Please note that some of the foods over there may contain processed sugar.

  2. Please note that some of the foods over there can contain processed sugar.

According Practical English by Michael Swan, the second one should not be said. I am not very sure about this argument.

I suppose that it is fine to say "something can be harmful"; if so, why is it not fine to say "something can contain a harmful ingredient", but "something may contain a harmful ingredient"?

  • In this context, can means is capable of. But, also in this context, it would be pointless to put can on a label—because food is capable of containing anything at all. It would be just as valid to say this food can contain arsenic. The sense required here is one of possibility in the specific context of likelihood, not capability. So, you have to use may. Another word that could be used is might. Commented May 12, 2020 at 4:33
  • @JasonBassford I see, but could'nt "can" be used to talk about the possibility as I mentioned in the question like, "this thing can hurt you, so be careful when working with it"
    – Cardinal
    Commented May 12, 2020 at 4:37
  • 1
    Strictly speaking, it's possible. That's certainly one dictionary sense of the word. And it's used in just that way in the this thing can hurt you sense. But it's not used that way when it comes to food labels. (Although smoking can kill you is used on cigarette labels.) If you want, you can call this an arbitrary way we've come to use the language. Even though can does also have that possible sense, it's just not applied in that way to food labels. I don't know why … Commented May 12, 2020 at 4:41

1 Answer 1


The difference as I see it is the same as @Jason Bassford was referring to: Can in this context indicates something very weak -- it indicates that something is technically not impossible, but gives no indication of whether or not that something can be expected. It is completely neutral about likelihood. May, on the other hand, indicates that there is some significant extent to which that something is to be expected. It indicates that there is a certain likelihood, enough so that a warning is warranted.

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