Original: Algae (or; singular alga, Latin for "seaweed") are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length.
Simplified: Though the prokaryotic Cyanobacteria (formerly referred to as blue-green algae) were included as "Algae" in older textbooks, this is outdated.