Parvum Opus (Latin for small work) is a weekly column on the English language, and more, that I've been writing since just before Christmas of 2002. I'm an English teacher, writer, and editor: one of those compulsive readers and proofreaders. In the Middle Ages, when the great universities were established in Europe, students studied the Trivium and the Quadrivium. The Trivium consisted of grammar, rhetoric, and logic. The Quadrivium consisted of arithmetic; geometry; music, harmonics, or tuning theory; and astronomy or cosmology. Someday, I may change Parvum Opus to Trivium Pursuit. My original intention was to write a short note on one point of English usage per week. It would be not just a grammar tip, but a comment on the way language is used and misused. The first issue was on the word "actionable," in which I explain why you do NOT want to create an "actionable business plan." But since language is always about something, I wrote about the substance as well as the form of language. I could not, for instance, ignore the Iraq war. My views on that and other public issues have shifted since that first year of writing, which lost me some friends and readers in subsequent years. A few years ago I shifted most of my political comments to my Cincinnati Independent Examiner column, at www.examiner.com/independent-in-cincinnati. Parvum Opus also includes a lot of comments, questions, information, and corrections from steady readers over the years. Sometimes they wrote the column for me, and I thank them. This volume even includes my poem about making mistakes.