Links and learning materials about the rules governing English diction and idiom

Diction, meaning “word choice,” is the term referring to the usage of specific individual words. Errors in diction typically involve a confusion between two similar words, like allusion and illusion.

Idiom refers to the conventional usage of set expressions. Although we often think of idioms as colorful, figurative expressions (e.g., “a few tacos short of a combo plate” to describe someone who is either stupid or crazy), the term actually has a much broader meaning. Any specific, fixed combination of words traditionally used to express an idea can be considered an idiom, such as “interested in” (not “interested on”).

Usage is the general term for highly specific rules about how we use words that are determined by convention (common or traditional practice) rather than the more generally applicable rules of grammar, such as those governing verb tense or subject-verb agreement. Rules of usage often have little to do with logic, and in fact can sometimes be illogical and inconsistent.

My extensive Common Errors in English Usage list is a compendium of diction and idiom errors that are often tested on the SAT, ACT, and other standardized tests and should be learned by any serious student or aspiring writer. It is a useful reference source for specific questions about usage, but it is also useful as a course of study. The browser version of the list linked here is a revised and expanded list of the PDF version that I posted here years ago. The list also has links to a series of companion quizzes that cover the contents of the list.

Related Resources

Common Errors in English Usage: An extensive list of specific errors in diction and idiom commonly made by native speakers of English

Common Errors Quizzes:
Quiz 1: A Entries | Quiz 1 PDF
Quiz 2: B Entries | Quiz 2 PDF
Quiz 3: C Entries | Quiz 3 PDF
Quiz 4: D – E Entries | Quiz 4 PDF
Quiz 5: F – H Entries | Quiz 5 PDF
Quiz 6: I Entries | Quiz 6 PDF
Quiz 7: J – L Entries | Quiz 7 PDF
Quiz 8: M – O Entries | Quiz 8 PDF
Quiz 9: P – Q Entries | Quiz 9 PDF
Quiz 10: R – S Entries | Quiz 10 PDF
Quiz 11: T – Z Entries | Quiz 11 PDF

Practical English Usage by Michael Swan: My go-to reference tome for many years regarding usage issues

4th Edition with online access code
4th edition | 3rd edition (Kindle)