means Plankton are the tiny organisms — plants, animals, and microbes — that drift along in the water without the power to swim against currents, forming the foundation of aquatic food webs.

from From the Greek 'planktos,' meaning 'wandering' or 'drifting,' itself from 'plazesthai,' to wander or be carried about. The German scientist Victor Hensen brought it into scientific use in the late 19th century to name these creatures that go wherever the water takes them — fittingly, a word for drifters that itself drifted from ancient Greek into modern biology.