alga

noun

al·​ga ˈal-gə How to pronounce alga (audio)
plural algae ˈal-(ˌ)jē How to pronounce alga (audio) also algas
: any of a diverse group of chiefly photosynthetic and aquatic plantlike organisms that range from unicellular to large multicellular forms, are typically classified as protists, and include the green, yellow-green, brown, golden-brown, and red algae in the eukaryotes and especially formerly the cyanobacteria in the prokaryotes

Note: While multicellular algae often resemble plants, they lack the true roots, leaves, and stems characteristic of vascular plants.

… the divers were witnessing the collapse of the delicate symbiotic relationship between the coral animals and the single-celled photosynthetic algae, called zooxanthellae, that normally flourish within them.Lucy Bunkley-Williams and Ernest H. Williams, Jr.
In the intertidal zone limpets and other mollusks graze on algae in the rocks.Roger Rosenblatt
Diatoms, the preeminent form of algae in most of today's freshwater and marine environments, need high concentrations of nutrients near the water's surface in order to bloom and form mats.Mrill Ingram
But the rapid decline of one of the pond's rare plants, a one-metre long giant freshwater alga called stonewort, has alerted scientists to the fact that changes are taking place at Hell Kettles.The Journal (Newcastle, England)
Giant kelp, the world's largest species of marine algae, is an attractive source for making biofuels.Diane Kim
algal adjective
algal cells
Stimulated by warm, still weather, algal blooms deoxygenate the water below. William Booth

Examples of alga in a Sentence

Recent Examples on the Web Instead, the alga survived and became a symbiotic partner to the protozoan, feeding it the fruits of its photosynthesis. Kevin Hartnett, Quanta Magazine, 6 July 2023 The adults, after all, have opaque bodies and spend most of their lives underground – conditions that are less than ideal for a light-dependent alga. Ed Yong, Discover Magazine, 5 Apr. 2011 Soon, all parts of each alga will be used. Hannah Hall, Washington Post, 9 Jan. 2023 Just as light is both a wave and a particle, the fungus and alga are both individuals and parts of a whole. Erica Gies, Scientific American, 1 June 2017 Every animal, plant, fungus and alga on the planet rose from the results of this old partnership. Ed Yong, Discover Magazine, 20 Jan. 2011 The alga’s heirs diversified. Elizabeth Kolbert, The New Yorker, 6 Dec. 2021 The alga draws energy from sunlight and produces sugars, which the bacterium uses as fuel. Ashley P. Taylor, Discover Magazine, 22 Sep. 2012 This is the first recorded example of an alga practicing an aquatic equivalent to pollination. Jack Tamisiea, Scientific American, 28 July 2022

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

Word History

Etymology

Latin, seaweed

First Known Use

circa 1527, in the meaning defined above

Time Traveler
The first known use of alga was circa 1527

Dictionary Entries Near alga

Cite this Entry

“Alga.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/alga. Accessed 12 Apr. 2024.

Kids Definition

alga

noun
al·​ga ˈal-gə How to pronounce alga (audio)
plural algae ˈal-(ˌ)jē How to pronounce alga (audio)
: any plant or plantlike organism (as a seaweed) that includes forms mostly growing in water, lacking a system of vessels for carrying fluids, and often having chlorophyll masked by brown or red coloring matter
algal adjective

Medical Definition

alga

noun
al·​ga ˈal-gə How to pronounce alga (audio)
plural algae ˈal-(ˌ)jē How to pronounce alga (audio) also algas
: any of a diverse group of chiefly photosynthetic and aquatic plantlike organisms that range from unicellular to large multicellular forms, are typically classified as protists, and include the green, yellow-green, brown, golden-brown, and red algae in the eukaryotes and especially formerly the cyanobacteria in the prokaryotes
algal adjective

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