alga
Pronunciation: /ˈalgə/
noun ( plural algae /ˈaldʒiː, ˈalgiː/)
- a simple, non-flowering, and typically aquatic plant of a large assemblage that includes the seaweeds and many single-celled forms. Algae contain chlorophyll but lack true stems, roots, leaves, and vascular tissue.
- Divisions Chlorophyta ( green algae), Heterokontophyta ( brown algae), and Rhodophyta ( red algae); some (or all) are frequently placed in the kingdom Protista

Origin:
mid 16th century: from Latin, 'seaweed'