n. pl. the·cae (-sē′, -kē′)
A case, covering, or sheath, such as the covering of the pollen sacs of an anther or the thick cell wall of certain dinoflagellates.
[Latin thēca, case, receptacle, from Greek thēkē; see dhē- in the Appendix of Indo-European roots.]
thecal (-kəl) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.