algae

[al-jee]

plural noun

singular

alga 

1. Microbiology.,  any of numerous groups of chlorophyll-containing, mainly aquatic, eukaryotic organisms ranging from microscopic single-celled forms to multicellular forms 100 feet (30 meters) or more long, distinguished from plants by the absence of true roots, stems, and leaves and by a lack of nonreproductive cells in the reproductive structures: classified into the six phyla Euglenophyta, Crysophyta, Pyrrophyta, Chlorophyta, Phaeophyta, and Rhodophyta.

algae

/ ˈældʒiː, ˈælɡəl /

plural noun

1. unicellular or multicellular organisms formerly classified as plants, occurring in fresh or salt water or moist ground, that have chlorophyll and other pigments but lack true stems, roots, and leaves. Algae, which are now regarded as protoctists, include the seaweeds, diatoms, and spirogyra

algae

1. Primitive organisms that contain chlorophyll but do not have structures, such as xylem and phloem, to transport fluids. Algae sometimes contain only a single cell, and nowadays they are not considered members of the plant kingdom.

Algae supply a considerable part of the world's oxygen.

The most familiar algae are the greenish scum that collects in still water.

Other Word Forms

• algal adjective

Word History and Origins

Origin of algae¹

First recorded in 1790–1800; from New Latin, plural of Latin alga “seaweed”

Word History and Origins

Origin of algae¹

C16: from Latin, plural of alga seaweed, of uncertain origin

Example Sentences

Some of these animals can photosynthesize like plants; some harvest algae and seawater to make calcium carbonate for their underwater castles; some produce their own light or glow in the dark.

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During the summer, these floating mats of brown algae collect in large amounts on beaches where they decay and release an unpleasant smell.

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People of all different ages play and splash in the pool, as if this is normal—as if the pool isn’t as big as a baseball field and holding water the color of algae.

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"We need to keep the pipes clean, and they eat the algae," Mr Richardson tells the BBC.

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It has suffered four significant marine heatwaves between 2016 and 2022, causing much of its coral to expel the algae which gives them life and colour - a process called bleaching, which is often fatal.

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Related Words

• seaweed