English Reference

Word

conjecture

Phoneticscon·jec·ture, stress on the second syllable

US/kənˈdʒɛkʃɝ/

UK/kəndʒˈɛktʃɐ/

Definitions

01an unproven guess

C1 · Advanced Uncountable noun Formal

n. an opinion or idea you form without having all the facts.

n. a conclusion or proposition based on incomplete evidence; a supposition that lacks definitive proof.

“The news report was based on conjecture rather than hard evidence.”

“The historian admitted that his theory about the king's disappearance was mere conjecture, as no contemporary documents survived the fire.”

02mathematical hypothesis

C1 · Advanced Countable noun Mathematics Technical

n. a mathematical statement that appears to be true but has not been proven by logic yet.

n. a mathematical proposition which has been conjectured to be true, but for which no proof has yet been found.

“The mathematician spent years trying to prove the famous conjecture.”

“Goldbach's conjecture remains one of the oldest and best-known unsolved problems in number theory and all of mathematics.”

Antonyms

03to guess

C1 · Advanced Formal

v. to form an opinion or reach a conclusion using only a little information.

v. to infer from inconclusive evidence; to propose a hypothesis without formal verification.

“Scientists conjecture that there may be water deep under the planet's surface.”

“Archaeologists conjecture that the site served as a ceremonial center, though the lack of artifacts makes a definitive conclusion impossible.”

Synonyms

speculatesurmisehypothesize

Antonyms

Usage

Uncountable when referring to the act of guessing; countable when referring to a specific guess or theory.

Real-World Examples

“His killing, which remained unsolved for decades, gave rise to fervent conspiracy theories and conjecture.”
The Guardian 15 Aug 2026
“Because not one of Custer’s men lived to tell the tale, exactly what happened next has been a matter of conjecture ever since, inspiring an almost infinite number of conflicting story lines.”
Smithsonian Magazine 24 Jun 2026
“The result shows that the conjecture is false in three dimensions and above, although the original two-dimensional version remains unsolved.”
ScienceDaily 6 Aug 2026

Etymology

From Old French, from Latin coniectūra (“a guess”), from coniectus, perfect passive participle of cōniciō (“throw or cast together; guess”), from con- (“together”) + iaciō (“throw, hurl”); see jet. Compare adjective, eject, inject, project, reject, subject, object, trajectory, deject, abject, surjection, bijection, interject. Compare typologically Russian прики́дывать (prikídyvatʹ) (akin to кида́ть (kidátʹ)).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Domains

LinguisticsMathematics

This entry

Exam level
CambridgeCambridgeCambridge English QualificationsThe exam suite from Cambridge University Press & Assessment, from A1 Movers up to C2 Proficiency. The benchmark names double as CEFR labels.C1 AdvancedIELTSIELTSInternational English Language Testing SystemThe 0–9 band test co-owned by the British Council, IDP, and Cambridge. Used for university entry, work, and migration.7.0–8.0TOEFL iBTTOEFL iBTTest of English as a Foreign Language, Internet-Based TestETS's academic English test, the standard route for US university admissions. Scored 0–120, with a 1–6 scale since 2026.1–6 scale: 5.0–5.595–113TOEICTOEICTest of English for International CommunicationETS's workplace English test, big in Japan and Korea. Listening & Reading scores 10–990 and tops out at C1.945–990EikenEikenTest in Practical English ProficiencyThe English proficiency test from the Eiken Foundation of Japan, widely taken by Japanese students. Grades run from 5 to 1, with Pre-1 and Pre-2 between them.Grade 1
Frequency
Frequent
Level
C1 · Advanced
Updated

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English Reference