[ thee-sis ]
/ ˈθi sɪs /
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noun, plural the·ses [thee-seez]. /ˈθi siz/.
a proposition stated or put forward for consideration, especially one to be discussed and proved or to be maintained against objections: He vigorously defended his thesis on the causes of war.
a subject for a composition or essay.
a dissertation on a particular subject in which one has done original research, as one presented by a candidate for a diploma or degree.
Music. the downward stroke in conducting; downbeat.Compare arsis (def. 1).
  1. a part of a metrical foot that does not bear the ictus or stress.
  2. (less commonly) the part of a metrical foot that bears the ictus.Compare arsis (def. 2).
Philosophy. See under Hegelian dialectic.
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Origin of thesis

First recorded in 1350–1400; Middle English, from Latin, from Greek thésis “a setting down, something set down,” equivalent to the- (stem of tithénai “to put, set down”) + -sis noun suffix; see -sis

historical usage of thesis

Thesis comes via Latin thesis from Greek thésis. There are only two meanings of thesis in Latin: in rhetoric, a general or abstract question (as opposed to a particular case), a proposition (the pure Latin term is propositum “something put forward”); and in poetry, the unstressed part of a metrical foot. However, Greek thésis has the opposite sense, the stressed part of a metrical foot. The Greek commentators explained thésis as the downward step of the foot (as of a marching soldier) or the lowering of the hand (as of a conductor indicating the accented beat). In Late Latin thesis meant “a lowering of the voice on an unstressed syllable” (its opposite is arsis, “a raising of the voice on a stressed syllable”). The sense “unstressed syllable or note” appears in English at the end of the 14th century and has been the accepted meaning since the 18th century in English poetry and music.
Thesis with the meaning “a proposition put forward to be discussed, proved, or defended” appeared in 1579; the more specific meaning “a dissertation required for an academic degree” dates from the second half of the 17th century. These meanings developed from the rhetorical sense in Latin and Greek.


1. antithesis, synthesis, thesis 2. dissertation, thesis
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use thesis in a sentence

British Dictionary definitions for thesis

/ (ˈθiːsɪs) /

noun plural -ses (-siːz)

Word Origin for thesis

C16: via Late Latin from Greek: a placing, from 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

Cultural definitions for thesis


The central idea in a piece of writing, sometimes contained in a topic sentence.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.