Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English


English definition of “alga”


noun [C usually pl]  /ˈæl·ɡə/ (plural algae  /ˈæl·dʒi/)
biology a very simple plant that grows in or near water and does not have ordinary leaves or roots
(Definition of alga noun from the Cambridge Academic Content Dictionary © Cambridge University Press)

Word of the Day


a good knowledge of something, or the fact that you know it so well

Word of the Day


Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More