noun, plural the·cae [thee-see] /ˈθi si/.
  1. a case or receptacle.
  2. Botany, Mycology.
    1. a sac, cell, or capsule.
    2. a sporangium.
  3. Anatomy, Zoology. a case or sheath enclosing an organ, structure, etc., as the horny covering of an insect pupa or the loose membrane covering the spinal cord.

Origin of theca

1655–65; < Latin thēca, from Greek thḗkē “case, cover,” akin to tithénai “to place, put”
Related formsthe·cal, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for thecal

Historical Examples of thecal

British Dictionary definitions for thecal


noun plural -cae (-siː)
  1. botany an enclosing organ, cell, or spore case, esp the capsule of a moss
  2. zoology a hard outer covering, such as the cup-shaped container of a coral polyp
Derived Formsthecal or thecate, adjective

Word Origin for theca

C17: from Latin thēca, from Greek thēkē case; related to Greek tithenai to place
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

thecal in Medicine


  1. Of or relating to a sheath, especially a tendon sheath.


n. pl. the•cae (-sē′, -kē′)
  1. A case, covering, or sheath, such as the outer covering of the cocoon of certain insects.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

thecal in Science


Plural thecae (thēsē′, -kē′)
  1. A case, covering, or sheath, such as the pollen sac of an anther, the spore case of a moss, or the outer covering of the pupa of certain insects.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.