Expert: Dan Smith - 1/7/2005

Question
Hello,
I work with an Hispanic man helping him learn English,and he helping me in Spanish. Today he asked me when to use "could" and "might".   How do I explain to him when to use the two words.  I told him when using "might", it means a possibility. And yet when I created the sentence below, I had to admit that both words indicated possiblity.  Example:

I might work tomorrow.
I could work tomorrow.

What is the grammar rule on use of these two words? Thank you!


Answer
In these two stand-alone sentences, they are pretty much interchangeable. If some context is added, then one might become preferable over the other. If, for instance, the issue is one of probabilty (there is a chance you might be called in to work tomorrow if you are needed), you would probably find "might" most appropriate.

If, on the other hand, the issue is one of permission to work (you are allowed to work and get paid for some extra time if you want to), then you might choose "could."

I can think of some other variations on this theme, and you probably can as well. The choice is not so much a matter of grammar as of nuanced definition in particular contexts. And in many cases it would not make much difference. These are the kinds of choices that nonnative speakers have real difficulty with, and they'll be more likely to make the nonstandard choice. I don't think I'd lose a lot of sleep over this one, though.

Hope this helps.