Original: Diatoms (Greek:  (dia) = "through" +   (temnein) = "to cut", i.e., "cut in half") are a major group of eukaryotic algae, and are one of the most common types of phytoplankton.
Simplified: Diatoms (Greek:  (dia) = "through" +   (temnein) = "to cut", i.e., "cut in half") are a big group of eukaryotic algae.