plank·​ton ˈplaŋ(k)-tən How to pronounce plankton (audio)
plural plankton also planktons
: the passively floating or weakly swimming usually minute organisms (such as dinoflagellates, diatoms, copepods, radiolarians, and larval crustaceans and fish) of a body of water

Note: An individual organism found in plankton is technically referred to as a plankter.

… photosynthesizing plankton will grow at their intrinsic rates until nutrients become limiting, light is reduced by shading, and grazing organisms become abundant enough to check the increase …W. H. Berger
Almost all marine invertebrates, such as corals, clams, and starfish, reproduce by releasing microscopic larvae that drift in the plankton for a period ranging from minutes to months.Randy Olson et al.
Dense schools of menhaden … pour through these waters, toothless mouths … slurping up plankton and detritus …H. Bruce Franklin
The prolific zebra mussels have extremely efficient filtering systems, removing enormous quantities of plankton from the water …Nelson Bryant
see also phytoplankton, zooplankton
planktonic adjective
Other planktonic forms are grazers—tiny animals that filter algae and other organic matter out of the water and consume it. Wyoming Wildlife

Examples of plankton in a Sentence

fish that feed mainly on plankton
Recent Examples on the Web Every May through November, giant manta rays come to feed, amassing by the hundreds, doing somersaults to catch plankton in their open mouths while snorkelers watch on in awe. Katie Lockhart, Robb Report, 9 May 2024 According to the New York Department of Environmental Conservation, sei whales eat 2,000 pounds of fish and plankton per day. CBS News, 8 May 2024 In addition to plankton dealing with ever-higher temperatures due to global warming, there’s also natural variability to consider here. Matt Simon, WIRED, 15 Feb. 2024 The significance of this is that up till now, the amount of carbon released to generate the PETM has been calculated from the aftereffects of the emissions—things like changes in ocean chemistry recorded in fossils of plankton that lived at the time. John Timmer, Ars Technica, 13 Jan. 2023 See all Example Sentences for plankton 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'plankton.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


German, from Greek, neuter of planktos drifting, from plazesthai to wander, drift, middle voice of plazein to drive astray; akin to Latin plangere to strike — more at plaint

First Known Use

1889, in the meaning defined above

Time Traveler
The first known use of plankton was in 1889

Dictionary Entries Near plankton

Cite this Entry

“Plankton.” Dictionary, Merriam-Webster, Accessed 19 Jun. 2024.

Kids Definition


plank·​ton ˈplaŋ(k)-tən How to pronounce plankton (audio)
: the floating or weakly swimming animal and plant life of a body of water
planktonic adjective

More from Merriam-Webster on plankton

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!