Coffee is the roasted seed of a fruit known as a coffee cherry.
This widespread misunderstanding is one for which the entire business must take responsibility. All coffee “beans” are seeds, but not all seeds are beans, and, surprise, for as long as anybody can remember, we’ve all been saying the incorrect thing!
Coffee is a seed that grows within a fruit on a tree, but it is not a bean. Because coffee plants do not belong to the Leguminosae family, they were never beans. But we still call them beans, and you can call them beans, and we can all be technically incorrect at the same time for the sake of general usage, and let’s just celebrate the myth’s survival!