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12.1 present and future ability and possibility can versus may (cont.) 3.
Can indicates certainty regarding the future.
4.
May have + past participle is used to indicate a deduction made about a past event.
Note the form can have + past participle does not exist.
5. Sometimes there is very little difference in meaning when
can and
may are
used in the affirmative form, though
can indicates greater certainty and is therefore preferred in definitions (last example below.
CAN MAY 4 Our sample was only small. Clearly, this
may have affected the results.
5 In our view,
having two systems can / may be a more reliable way for dealing with this problem. In our view, having two systems
can / may be a more reliable way for dealing with this problem.
5 Dogs
can / may eat up to 5
kg of food per day, as can be seen in Table 4. Dogs
can / may eat up to 5 kg of food per day, as can be seen in Table 4.
5
A university can be defined as a place of advanced learning. A university
may be defined as a place of advanced learning.
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12.2 impossibility and possibility cannot versus may not 1.
Cannot indicates impossibility (i.e. a certain event or scenario is not possible.
2.
May not indicates there is a possibility that something will not happen
(i.e. a certain event or scenario is not likely.
3.
Cannot have + past participle indicates a deduction regarding the impossibility of a past event.
4.
May (not) have + past participle is used
to speculate about the past, particularly in the Discussion
might have and
could have can also be used in the same way. Note the form
can have + past participle does not exist.
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