A friend on Facebook mentioned a nice little naming problem I had not been aware of in years of computer science:
We are always drawing tree structures with the root on top, sometimes with the root on the left, but almost never with the root where it belongs (according to biologists) in a tree: at the bottom.
In a comment, a kind soul suggested viewing the usual top-down trees as Christmas trees, and thus naming the root “star“. Should I ever teach data structures again, I will use this one.
And the start of a tree drawn from left to right could be … the source (of a creek, a river).