Czuch Chuckers: But you may still say "a pencil" if you are indifferent to the number of pencils you receive; that is, if you want at least one pencil. Of course, if one pencil will not do, you won't say "a pencil", you will specify the number that you need. "A pencil" is to be used only when you want exactly one, OR are indifferent to the number.