We have dirty isomers and we have enantomers. So just a moment ago, we said enantomers are those isomers that are mirror images of one another. Now, if it's not an enantomer, then it is a dioisomer. So we have two categories of isomers, either enantomers or dioisomers. So essentially, if two sugar molecules have the same exact molecular formula and they are not enantomers, then that means they must be diamers. And these are two examples of dioisomers.