Breakfast is whatever the first thing I eat after waking up. Given that today I woke up, caught my bus to go shopping (left around 1 pm) and got back 3 hours later, my breakfast today was a small bag of chili-flavored Doritos and Coke Zero.
Cereal is something my dad always preferred as a bedtime snack and he convinced me that this was a Good Thing.
Back in the days when I went to school, breakfast while living with my dad and his girlfriend was cereal, toast, and milk.
Breakfast in the early days of living with my grandparents was porridge (rolled oats), brown sugar, and milk.
After a few years of that, I asked my grandmother if I could have something different. She asked what I'd like, so scrambled eggs and milk became my daily breakfast. Egg nog was a seasonal treat (at Christmas and Easter).
As time went on and I started my home typing business, it soon became necessary to throw traditional breakfast out the window. Enough clients had an early morning pickup for early morning classes, and it was easier to go to a schedule of sleep between about 6 am-1 pm (my grandmother handled any pickups and drop-offs during that time), wake up and eat something - usually whatever was for lunch, normally soup and/or a sandwich or meat and veggies, watch my soap opera at 2 pm, and then type whatever pile of papers and resumes, etc. were waiting. I kept at it until it was finished - however many hours it took, with bathroom breaks. I'd usually finish sometime between 3-6 am, and if it was winter, I'd clear whatever ice and snow were on the porch and sidewalk, and then go to bed. So there were no normal breakfasts for those years.
The thing is, when you don't have much of a structured day and you're a night owl anyway, the idea of "breakfast" and certain things you would traditionally eat just seems unimportant.
It's a bit frustrating to explain this to doctors who can't wrap their minds around the idea of "I'm normally asleep at the time you're telling me to take this pill, and no, I can't just get up earlier." That's not how I'm wired.
But I do like eggs, toast, sausages, porridge (prefer cream of wheat with honey), and I still like milk.
There was a time at the nursing home when the nurses were expressing frustration over my dad not wanting to eat breakfast. So I told them to make some porridge, put some raisins in it, add some cinnamon and some milk, and tell him it was dessert - because that's the kind of thing my grandmother sometimes served for an afternoon snack. I told them he liked dessert, so he'd probably eat it. Just don't try it at breakfast time because he was also a night owl and definitely not in the mood for breakfast any time before noon.