algae

[al-jee] /ˈæl dʒi/

plural noun, singular alga

[al-guh] /ˈæl gə/ (Show IPA)

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.

Compare blue-green algae.

Origin

< Neo-Latin, plural of Latin alga seaweed

Related forms

algal, adjective

Examples from the web for algae

The algae floating in the sea are microscopic plants of great consequence on a global level.
Green algae do better than red and brown algae in the strong light of shallow water.
When the algae die and decompose, the water is depleted of oxygen.
They are toothless herbivores who live off the plants and algae in the river.
Every living thing-from one-celled algae to giant blue whales-needs food to survive.
The plants and algae deplete the available oxygen supply.
Even the bands on the abalone's shell bear evidence of water conditions, and the abundance of the algae and kelp it feeds upon.
All she had for water was a small cistern with rain water in it, covered with algae.
On living whales, it's typically green with algae and alive with sea lice at its base.
Marine algae are tiny plants, many of them microscopic in size.

British Dictionary definitions for algae

algae

/ˈældʒiː/

plural noun (sing) alga (ˈælɡə)

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

Derived Forms

algal (ˈælɡəl) adjective

Word Origin

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

Word Origin and History for algae

(plural), 1794, from alga (singular), 1550s, from Latin alga "seaweed," of uncertain origin, perhaps from a PIE root meaning "to putrefy, rot."

algae in Medicine

algae al·gae (āl'jē)
pl.n.
Any of various chiefly aquatic, eukaryotic, photosynthetic organisms, ranging in size from single-celled forms to the giant kelp.

algae in Science

alga

(āl'gə)
Plural algae (āl'jē)
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.

algae in Culture

algae [(al-jee)]

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.

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

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