noun
sea lettuce
Refers to green algae of the genus Ulva, often found in intertidal zones and used in some Japanese dishes.
海岸の岩にアオサがたくさんついていた。
A lot of sea lettuce was attached to the rocks on the shore.
アオサは味噌汁の具として使われることがある。
Sea lettuce is sometimes used as an ingredient in miso soup.
Hiragana spelling is also used.
アオノリ (green laver) is a different type of green algae, often dried and used as a condiment, while アオサ is a leafy seaweed.
The name likely derives from 青 (ao, 'blue/green') and 藻 (mo, 'algae'), but the exact derivation is uncertain.