A rivulet is a very small stream of water, much tinier than a creek or brook. Picture the thin trickle that runs down a windshield during a light rain, or the tiny channel of water that flows down a hillside after a storm. That's a rivulet.

The word often appears in nature writing and poetry because it captures something delicate and specific. After a heavy rain, you might see rivulets flowing across a playground or parking lot, each one finding its own path to lower ground. When you wash your hands, rivulets of soapy water run down your wrists. On a hot day, a rivulet of sweat might trickle down someone's forehead.

Rivulets can join together to form larger streams, which eventually become rivers. Think of them as water's first step in a long journey: a small beginning that grows into something much bigger. The word suggests something gentle and flowing rather than powerful or rushing, like comparing a whisper to a shout.