Algae

Part of speech: noun

Pronunciation: /ˈæl.d͡ʒi/

Definitions

1. A collection of simple, often aquatic life forms capable of photosynthesis, which can be unicellular or multicellular and play vital roles in aquatic environments
2. Various photosynthetic organisms living primarily in water, which can range from microscopic cells to larger species like seaweeds and are essential to ecological balance
3. Primitive plant-like organisms that produce oxygen through photosynthesis and inhabit water environments; simple photosynthetic organisms often forming slimy or filamentous growths ; diverse aquatic life forms that convert sunlight into energy and serve as a base for many food chains

Etymology: "Algae" is the plural of "alga," a Latin word meaning seaweed or a similar water growth. English took the Latin form directly rather than through French, so the Latin plural has stayed in use: a single organism is an "alga," and a group of them is "algae." The word has no cousin in other familiar English vocabulary, and it has kept its Latin meaning of plants growing in water, from seaweed to the microscopic cells that drift in ponds and oceans. Because "algae" is a plural, the English form is worth noticing. Speakers who treat it as a singular ("an algae") are reusing an English pattern that the Latin grammar does not support. Scientists keep the plural and the singular distinct, which is why a pond scum can be called "algae" in the plural and "alga" for one cell.

Synonyms: seaweed, plankton, phytoplankton, microorganisms, cyanobacteria