Is a small brook a rill?

Yes, a small brook can be considered a rill, as both terms refer to small, flowing bodies of water. A rill typically describes a tiny stream or channel formed by the flow of water, often found in landscapes where water runoff occurs. While "brook" usually refers to a slightly larger watercourse, the distinction can vary regionally. Therefore, in some contexts, a small brook may indeed be classified as a rill.