plankton

American  

[plangk-tuhn] / ˈplæŋk tən /

noun

1. the aggregate of passively floating, drifting, or somewhat motile organisms occurring in a body of water, primarily comprising microscopic algae and protozoa.

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plankton British  

/ plæŋkˈtɒnɪk, ˈplæŋktən /

noun

1. the organisms inhabiting the surface layer of a sea or lake, consisting of small drifting plants and animals, such as diatoms Compare nekton

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plankton Scientific  

/ plăngk′tən /

1. Small organisms that float or drift in great numbers in bodies of salt or fresh water. Plankton is a primary food source for many animals, and consists of bacteria, protozoans, certain algae, cnidarians, tiny crustaceans such as copepods, and many other organisms.

2. Compare benthos nekton

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Other Word Forms

• planktonic
  adjective

Etymology

Origin of plankton

1890–95; < German, special use of neuter of Greek planktós drifting, equivalent to plang-, variant stem of plázesthai to drift, roam, wander + -tos verbid suffix

Explanation

If you set your pet goldfish free in a lake, he might dine on plankton instead of the food you sprinkle in his tank every day. Or, more likely, he might be dinner for a bigger fish. Lakes, seas, and oceans are full of plankton, most of which is so small it can't be seen without a microscope. Anything that floats near the surface is considered to be plankton, whether it's an animal, plant, or something smaller like bacteria, and it's one source of food for fish and whales. The Greek root, planktos, means "wandering or drifting."

Example Sentences

See Examples For:

plankton

"This includes sea temperatures, the availability of plankton for feeding, which peaks during the summer months when it is warmer, and ocean currents."

From BBC ● Jul. 28, 2026

The natural phenomenon is caused by bioluminescent plankton, tiny creatures floating in the sea that have the ability to emit light when disturbed by a predator or motion.

From BBC ● Jun. 25, 2026

In past strong El Niños, scientists have observed decreased plankton — an important food source for marine animals — and an increased probability of harmful algal blooms.

From Los Angeles Times ● Jun. 15, 2026

It was a small, worm-like animal that spent most of its time in one place, feeding by filtering plankton from seawater.

From Science Daily ● Apr. 27, 2026

Not enough to try a plankton burger, but enough for a taste.

From "The Voyage Of The Frog" by Gary Paulsen