green algae

American  

plural noun

1. any grass-green, chiefly freshwater algae of the phylum Chlorophyta, often growing on wet rocks, damp wood, or on the surface of stagnant water.

---

green algae British  

plural noun

1. the algae of the phylum Chlorophyta, which possess the green pigment chlorophyll. The group includes sea lettuce and spirogyra

---

Etymology

Origin of green algae

First recorded in 1900–05

Example Sentences

Now, because bright green algae keeps reappearing every year around this time, Toledo must always be prepared for such outbreaks.

From Salon • Aug. 16, 2025

It could also cause harmful algae to grow out of control, creating wide patches of green algae that can poison other life.

From BBC • May 21, 2025

There’s a faucet on the eastern end of the campground where water from the creek is piped, but upon my arrival, the trough where the water came out was covered in thick green algae.

From Los Angeles Times • May 13, 2025

But as further specimens came to light, Dr Harvey identified similarities with modern green algae that live floating in the plankton of ponds and lakes.

From Science Daily • Oct. 25, 2023

And as far down as I could see, their sides consisted of green algae.

From "Life of Pi" by Yann Martel