thesis

UK: /ˈθiːsɪs/ US: /ˈθisɪs/ ,(thē′sis)

Inflections of 'thesis' (n): npl: theses

WordReference Random House Learner's Dictionary of American English © 2026

the•sis /ˈθisɪs/   n. [countable] , pl. -ses /-siz/ .

1. a statement for consideration, esp. one to be argued for or against:
   The candidate's thesis was that big government spent too much money wastefully.
2. a subject for a composition or essay:
   Your essay needs a clear thesis.
3. a formal paper reflecting original research on a subject, esp. one presented by a candidate for an advanced degree, as a master's degree.

See -thes-.

WordReference Random House Unabridged Dictionary of American English © 2026

the•sis  (thē′sis), n., pl. -ses (-sēz). 

1. a proposition stated or put forward for consideration, esp. one to be discussed and proved or to be maintained against objections:
   He vigorously defended his thesis on the causes of war.
2. a subject for a composition or essay.
3. a dissertation on a particular subject in which one has done original research, as one presented by a candidate for a diploma or degree.
4. Music and Dance the downward stroke in conducting;
   downbeat. Cf. arsis (def. 1).
5. Poetry [Pros.]
   • a part of a metrical foot that does not bear the ictus or stress.
   • (less commonly) the part of a metrical foot that bears the ictus. Cf. arsis (def. 2).
6. Philosophy See under Hegelian dialectic. 

• Greek thésis a setting down, something set down, equivalent. to the- (stem of tithénai to put, set down) + -sis -sis
• Latin
• Middle English 1350–1400

Synonyms

• 1. theory, contention, proposal.

Collins Concise English Dictionary © HarperCollins Publishers::

thesis / ˈθiːsɪs/ noun ( -ses / -siːz/)

1. a dissertation resulting from original research, esp when submitted by a candidate for a degree or diploma
2. a doctrine maintained or promoted in argument
3. a subject for a discussion or essay
4. an unproved statement, esp one put forward as a premise in an argument

Etymology: 16th Century: via Late Latin from Greek: a placing, from tithenai to place