Runlets are small, shallow streams or rivulets that flow through the earth. There are a few different synonyms for the word runlets, including brooks, creeks, streams, rivulets, and even rills. Brooks typically refer to larger, wider streams that flow along a gentle slope, while creeks can be larger or smaller and may be found in more rugged terrain. Streams generally refer to a flowing, continuous body of water, while rivulets and rills tend to be the smallest of the group, describing tiny channels or streams of water that may even flow underground. Regardless of which term is used, these synonyms all describe small, moving bodies of water that can add to the beauty and natural diversity of the landscape.