Seaweed
"Seaweed" is a colloquial term and lacks a formal definition. A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups do not have a common multicellular ancestor, the seaweed are in a polyphyletic group. In addition, some tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered to be seaweed.
Alaria (alga)
In Ireland, Scotland, Greenland, Iceland, Denmark, and the Faroe Islands, the midrib is removed, and the blade and sometimes the leaflets are eaten, although it is not commercially available. It is more commonly eaten in the Far East (China, Japan, and Korea), where seaweed consumption is much more popular than in the West. Seaweeds are considered to be highly nutritious, because typically they are low in fat, and have vitamins and minerals in amounts comparable or superior to terrestrial vegetables. "Alaria esculenta", in particular, is an excellent source of protein and iodine.