Algae Is Plural, and Its Singular Is Rare
Algae are simple photosynthetic organisms. They are not plants, they produce a large share of the world's oxygen, and the singular alga is seldom used.
Algae are simple organisms that photosynthesise, from single cells to giant kelp. They are not plants, and they matter more than their reputation suggests: marine algae and other ocean photosynthesisers are usually credited with producing roughly half the oxygen in the atmosphere. The Latin singular *alga* meant seaweed, and English almost never uses it.
- Simple photosynthetic organisms. *Green algae.*
- Alga — the rare singular. *A single alga.*
- Algal bloom — a rapid growth. *A toxic algal bloom.*
- Seaweed — large marine algae. *Edible seaweed.*
- Algal — the adjective. *Algal growth.*
Word forms
| Form | Word | Example |
|---|---|---|
| Plural | algae | Algae are simple. |
| Singular | alga | A single alga. |
| Adjective | algal | An algal bloom. |
| Latin | alga | Seaweed. |
| Related | phytoplankton | Ocean phytoplankton. |
- Algae are not plants.Takes a plural verb.
- The algal bloom closed the beach.The adjective.
- Kelp is a large brown alga.The singular, in scientific writing.
Why algae are not plants
- No roots, stems or leaves — no true tissue organisation
- Not one group — algae are spread across several unrelated lineages
- Some are bacteria — cyanobacteria were once called blue-green algae
- Land plants evolved from one particular group of green algae
- The word is a convenience, not a scientific classification
Latin *alga*, seaweed, of uncertain origin. English took the plural in the 1550s and the singular has never been common.
Is algae singular or plural?
Plural. The singular is alga, but almost nobody uses it outside scientific writing.
Do algae really make half the world's oxygen?
Ocean photosynthesisers, mostly microscopic algae and cyanobacteria, are generally credited with about half of atmospheric oxygen production.