alga

Everyday

1. An alga is a single simple plant-like living thing that grows in water or damp places and makes food from sunlight; it has no roots, stems, leaves or flowers. tree →
2. Usually the word is used in the plural, algae: the green slime in ponds, the green on fish tanks, and seaweeds are all algae. tree →

In the lessons

In science lessons algae are producers at the start of water food chains and make much of the world's oxygen. Too much algae can turn a pond green and harm fish (an «algal bloom»). In everyday life algae make rocks, pools and fish tanks slippery. Phrases: «algae grow», «green algae», «algal bloom».

Examples

• Algae made the pond look green. tree →
• One tiny alga can only be seen under a microscope. tree →
• Seaweed is a kind of algae. tree →
• Algae make food from sunlight like plants. tree →
• We cleaned the algae off the fish tank glass. tree →
• Watch out, the rocks are slippery with algae. tree →
• Some blue-green algae are poisonous to dogs. tree →
• Fish and tadpoles eat algae. tree →

Note

Irregular plural: one alga, many algae (say «AL-guh», «AL-jee» or «AL-gee»). «Algae» is far more common; «alga» is the singular, mostly in science. Myth: algae are not exactly plants; scientists put them in their own groups. Safety: keep pets out of water with a thick green or blue scum.