thesis

noun

the·​sis ˈthē-səs 

British especially for sense 3 ˈthe-sis

plural theses ˈthē-ˌsēz 

1

: a dissertation (as by a candidate for an academic degree) presenting results of original research and usually providing evidence to support a specific view

2

a(1)

: an idea put forth for discussion or proof : hypothesis

… a decade or more before John Tyndall began to explore the thesis that slight changes in the atmosphere's composition could cause climatic variations.

—Leo Hickman

(2)

: a central idea or theme (as of an artistic work)

The song's hook … speaks to the album's thesis …

—Bobby Olivier

b often thesis statement

(1)

: a statement that introduces the thesis or main idea of a piece of writing

the report's opening thesis

A compelling thesis statement forms the backbone of your essay, expressing the main argument or point of view.

—Helen Garcia

(2)

: a statement of the central idea or theme (as of an artistic work)

… "The future sucks" might as well be the movie's thesis …

—Dan Caffrey

… Deanna … delivers the line of the night: "I want to live." That really is the thesis statement of the episode.

—John Saavedra

3

a(1)

: the unstressed part of a poetic foot especially in accentual verse

(2)

: the longer part of a poetic foot especially in quantitative verse

b

: the accented part of a musical measure : downbeat compare arsis

4

: the first and least adequate stage of dialectic compare synthesis

Did you know?

In high school, college, or graduate school, students often have to write a thesis on a topic in their major field of study. In many fields, a final thesis is the biggest challenge involved in getting a master's degree, and the same is true for students studying for a Ph.D. (a Ph.D. thesis is often called a dissertation). But a thesis may also be an idea; so in the course of the paper the student may put forth several theses (notice the plural form) and attempt to prove them.

Synonyms of thesis

• argument
• contention
• assertion
• hypothesis
• theory

Examples of thesis in a Sentence

She wrote her thesis on Renaissance Nativity scenes.

a master's thesis on the effects of global warming

New evidence supports his thesis.

We disagreed with the basic thesis of the report.

The book's central thesis is that propaganda influences the masses in important ways.

Recent Examples on the Web

Read more about that here and check out theses photos of the behemoth that carries rockets around the space center. —Roger Simmons, The Orlando Sentinel, 18 Mar. 2026

Now, think of that with gasoline — enough material for a master’s thesis in human misbehavior. —Patt Morrison, Los Angeles Times, 18 Mar. 2026

Word of de Broglie’s thesis spread, though hardly anyone actually read it. —Tim Folger, Scientific American, 16 Mar. 2026

In a way, Smalls is challenging the thesis of Mutiny. —George Packer, The Atlantic, 16 Mar. 2026

Word History

Etymology

in sense 3, Middle English, lowering of the voice, from Late Latin & Greek; Late Latin, from Greek, downbeat, more important part of a foot, literally, act of laying down; in other senses, Latin, from Greek, literally, act of laying down, from tithenai to put, lay down — more at do

First Known Use

14th century, in the meaning defined at sense 3a(1)

Rhymes for thesis

• rhesus
• amniocentesis
• spondylolisthesis
• cytokinesis
• paracentesis
• plasmapheresis
• enuresis
• pollicis

Kids Definition

thesis

noun

the·​sis ˈthē-səs 

plural theses ˈthē-ˌsēz 

1

: a statement put forth for discussion or proof : hypothesis

2

: a long essay presenting the results of original research