• synonyms


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.
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Origin of theca

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

Examples from the Web for theca

Historical Examples

  • But in Greek theca (, θήκη) is a place to put something, a receptacle.

    The Hindu-Arabic Numerals

    David Eugene Smith

  • The costae, longitudinal ribs or rows of spines on the outer surface of the theca.

  • Horizontal plates or floors found in some Corals, extending across the cavity of the "theca" from side to side.

  • This elastic ring is a continuation of the stalk of the theca, which always bursts on the opposite side.

  • This theca grows in the direction of the apex of the sicula, to which it adheres by its dorsal wall.

British Dictionary definitions for theca


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
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Derived Formsthecal or thecate, adjective

Word Origin

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

theca in Medicine


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

theca 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.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.