Breakfast, lunch, dinner for me. I thought "supper" was a British thing for a long time. Time varies quite a bit - I am an insomniac and sometimes start my day at 2AM, so I eat at all sorts of odd times.
The animals know "hungry". When it's about food-time for the pets I will ask, "Are you guys
hungry?" and chaos erupts as the dogs bark to let me know that yes indeed, they
are hungry; and the cat goes racing to his bowl to yowl at me until the bowl is full.