1. Any of various small chiefly freshwater branchiopod crustaceans of the order Cladocera, having a bivalve carapace and typically swimming with jerking flealike motions, and including the daphnias. Also called cladoceran.
2. Any of various other small aquatic crustaceans, such as some copepods, that swim with a similar motion.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.