What is the difference between "can be" and "may be"?

  1. Analysing reports of investigations may be observed...
  2. Analysing reports of investigations can be observed...
  • 2
    As a general rule, I don't want to close questions about differences between auxiliary verbs as entirely answerable by a dictionary. They're tricky, and too often there are gotchas waiting to trick learners, even advanced ones. Even though this particular case is fairly straightforward, I think it should be left open.
    – user230
    Commented Mar 26, 2014 at 22:55
  • The Q&A is designed so the poor soul in need of Google gets a simple and readable format instead of a cryptic dictionary. This serves that purpose. Why it's on the 'close-pending' list I have no idea.
    – MMJZ
    Commented Mar 30, 2014 at 19:25

3 Answers 3


"Can" simply means that the observation is possible. There is no reason for it to happen, but it is a possibility. In this context, it doesn't give any indication that the observation is likely to happen.

"May" is more direct. It defines a possibility that is more likely to happen, as the observation could be actively made to happen. It can also define something being given permission to happen: that statement is giving 'permission' for the observation to happen, regardless of whether its possible.


The first thing to say is that the use of modal verbs is a complicated subject, since a given modal verb can have different uses, and different modal verbs may have a similar use.

The following is based on the advise given in "Science Research Writing for Non-Native Speakers of English". This book lists the following uses for can and may:


This software can distinguish between different languages

Until 18 months a child cannot use symbols to represent objects


A rubber seal can be useful for this purpose

A rubber seal cannot be useful for this purpose

A rubber seal may be useful for this purpose

A rubber seal may not be useful for this purpose


It is clear that contamination cannot be due to the presence of seawater in the pipe


MMJZ gave you a good answer. I suggest you taking that one. I'll make a complement here.

By and large, "Can" represents a theoretical possiblity while "May" represents a factual possiblity.

Let's say, when you discuss the local weather with your friends,

If your friend says that it can be quite cold there in winter, what he says is just a general view of what the weather is usually like in winter. He is not predicting whether it's cold or warm in winter that year.

However, if he says that it may be quite cold there in winter, He is predicting from past experience that it's likely to be cold in winter that year.

  • Please supply the complete sentences. The portions you have supplied do not seem to make sense. Or rather, they seem to set up a five-phase progression. 1) something happens 2) it is investigated 3) reports are made of the investigations 4) the reports are analysed 5) the analyses are "observed" . Is it really that complicated? Commented Jan 11, 2015 at 8:40
  • By and large, "Can" represents a theoretical possiblity while "May" represents a factual possiblity. This explanation (if correct) is the most brilliant one that I've ever seen on this subject.
    – user166967
    Commented Feb 14, 2023 at 16:29

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