The word then is a common and useful word for connecting ideas in a sentence. Unfortunately, problems can arise from not understanding exactly what role — or what part of speech — then plays in a given situation. There are four options for then, though some writers try to shoehorn it into a fifth option.
May I Quote You on That? by Stephen Spector (Oxford University Press) is a new grammar and usage guide for the layperson, that is, anyone who needs to write well without necessarily being a professional communicator. For the professional writer or editor with at least some experience and training, “grammar for the masses” books are often of limited use.
I think all editors, at some point in their careers, go through a "Grammar Police" phase during which they offer unsolicited (and sometimes unsubstantiated) advice about how to "correctly" use a particular phrase, pronounce a particular word, or use a particular idiom. I know I did. It's an annoying phase — not for the editors, but for everyone around them — and one hopes they grow out of it quickly.
The singular they might just be 2015’s word of the year. As questions of transgender rights and gender equity continue making news, editors are feeling the need for a gender-neutral pronoun—and hotly debating solutions.
What you learned in English class will help you with syntax about as much as what you learned in driving lessons will help you with mechanics—you get by fine until one day you find yourself stopped in the middle of a sentence with smoke coming out from under the hood. In this seminar, we’re going to learn how to take apart sentences the way a mechanic takes apart an engine.