alga

American  

[al-guh] / ˈæl gə /

noun

algae, plural algas plural

1. any organism belonging to one of the numerous groups of algae.

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alga Scientific  

/ ăl′gə /

algae plural

1. Any of various green, red, or brown organisms that grow mostly in water, ranging in size from single cells to large spreading seaweeds. Like plants, algae manufacture their own food through photosynthesis and release large amounts of oxygen into the atmosphere. They also fix large amounts of carbon, which would otherwise exist in the atmosphere as carbon dioxide. Algae form a major component of marine plankton and are often visible as pond scum and blooms in tidal pools. Land species mostly live in moist soil and on tree trunks or rocks. Some species live in extreme environments, such as deserts, hot springs, and glaciers. Although they were once classified as plants, the algae are now considered to be protists, with the exception of the cyanobacteria, formerly called blue-green algae. The algae do not form a distinct phylogenetic group, but the word alga serves as a convenient catch-all term for various photosynthetic protist phyla, including the green algae, brown algae, and red algae.

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Other Word Forms

• alga-like
  adjective
• algal
  adjective
• antialgal
  adjective
• non-algal
  adjective

Example Sentences

You may never have heard of this single-celled alga, but sailors and fishermen know its effect very well: the P. lunula algae are the organisms that occasionally make the see glow blue.

From Science Daily • Nov. 18, 2024

Blue-green algae is not actually an alga but rather a type of bacteria called cyanobacteria.

From BBC • Jul. 10, 2023

This is the first recorded example of an alga practicing an aquatic equivalent to pollination.

From Scientific American • Jul. 28, 2022

In the case of Gracilaria, however, things are more complicated: The female alga doesn’t release its egg cells, but keeps them inside funnel-shaped filaments.

From Science Magazine • Jul. 27, 2022

She is curious; she wants to know the difference between an alga and a lichen, a Diplodon char- ruanus and a Diplodon delodontus.

From "All the Light We Cannot See" by Anthony Doerr