In Common Errors in English Usage there are more than 1000 explanations for those errors that we usually make when using the English language.
As words are alphabetically sorted, it’s very easy searching through them. For instance, the explanation for the difference between backup and back up is:
To “back up” is an activity; “back up your computer regularly”; “back up the truck to the garden plot and unload the compost.”
A “backup” is a thing: “keep your backup copies in a safe place.” Other examples: a traffic backup, sewage backup, backup plan, backup forces.”
Older writers often hyphenated this latter form (“back-up”), but this is now rare.
As you can see, the explanations are clear and they also include examples that help understanding them better.
This comprehensive list of common errors has been made by Paul Brians, Emeritus Professor of English Washington State University. Thanks very much Mr. Brians.
Link : Common Errors in English Usage