I read on Purdue OWL names of languages/nationalities, names of sports and names of academic subjects do not require articles. But what are the other situations?
To be more specific, I saw the sentence "I'd been sitting here for 10 minutes before class started" in a grammar book, and I wonder why there was no article in front of class.
When I asked the writing lab, I got the answer that it's convention. I got another example from the person who answered my question, saying other common usages including "I'm waiting for dinner to start" or "Let's leave after dessert" are both correct.
Is it just convention? Is there any rule behind it? Thank you!!