English – How to Use "Can" and "May" Correctly in your Technical Documents

© 2010 Ugur Akinci
It’s easy to remember the correct way of using “can” and “may” in your technical documents:
CAN expresses the ABILITY to do something. MAY has to do with the PERMISSION to do it or the POSSIBILITY of something happening.
For example:
ORIGINAL: “The circuitboard can overheat.”
[Of course; just like ANYTHING can overheat under the right conditions. But will it? That’s the real question here. And if it will, under what conditions? That’s what your readers would like to know.]
BETTER: “If you run the regulator nonstop for over 6 hours the circuitboard may overheat.”
[Now we know that the circuitboard will probably overheat if we run it for over 6 hours. At this point we know that that is POSSIBLE and thus we take precautionary measures. For example, we don’t run the regulator that long and shut it off before 6 hours.]
If however you’re 100% sure that the circuitboard WILL overheat, then say so:
EVEN BETTER: “The circuitboard will overheat if the regulator is run nonstop for over 6 hours.”
Another example:
“You can configure the server this afternoon.” [You have the ability to do it.]
“You may configure the server this afternoon.” [You have the permission to do it.]