Any of several divisions of simple
photosynthetic organisms, especially certain
thallophytes, variously one-celled,
colonial, or
filamentous, containing
chlorophyll and other
pigments (especially red and brown), and having no
root,
stem, or
leaf. Algae are found in
water or
damp places, and include
seaweeds and
pond scum.
Singular: alga