algae vs. seaweed

algae

[ al-jee ]show ipa

plural noun,

1. any of numerous groups of chlorophyll-containing, mainly aquatic, eukaryotic organisms ranging from microscopic single-celled forms to multicellular forms 100 feet (30 meters) or more long, distinguished from plants by the absence of true roots, stems, and leaves and by a lack of nonreproductive cells in the reproductive structures: classified into the six phyla Euglenophyta, Crysophyta, Pyrrophyta, Chlorophyta, Phaeophyta, and Rhodophyta.

seaweed

[ see-weed ]show ipa

noun

1. any plant or plants growing in the ocean.
2. a marine alga.