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Definitions

sure

[shoor, shur] / ʃʊər, ʃɜr /
ADJECTIVE
certain, definite
Synonyms
STRONGEST
assured clear confident convinced positive
WEAK
abiding changeless constant convincing decided doubtless enduring firm fixed for a fact free from doubt genuine incontestable incontrovertible indisputable indubitable never-failing persuaded real satisfied set steadfast steady telling unchangeable unchanging uncompromising undeniable unequivocal unfailing unfaltering unqualified unquestionable unquestioning unshakable unshaken unvarying unwavering valid
Antonyms
STRONGEST
doubtful uncertain unsure
WEAK
doubted dubious humbled indefinite swerving unconfident unself-confident unsteady variable wavering wobbly
ADJECTIVE
physically stable
Synonyms
STRONGEST
fast safe strong
WEAK
firm fixed secure solid staunch steady
Antonyms
WEAK
doubted doubtful dubious humbled indefinite swerving uncertain unconfident unself-confident unsteady unsure variable wavering wobbly
ADJECTIVE
inevitable
Synonyms
STRONGEST
assured certain
WEAK
bound guaranteed indisputable ineluctable inerrant inescapable infallible irrevocable surefire unavoidable unerring unfailing
Antonyms
STRONGEST
doubtful doubting hesitant uncertain
WEAK
doubted dubious humbled indefinite swerving unconfident unself-confident unsteady unsure variable wavering wobbly
ADJECTIVE
self-confident
Synonyms
STRONGEST
assured certain confident decisive positive
WEAK
arrogant composed decided self-assured self-possessed
Antonyms
STRONGEST
doubtful doubting hesitant indefinite uncertain unsure
WEAK
doubted dubious humbled swerving unconfident unself-confident unsteady variable wavering wobbly

Usage

What are other ways to say sure? Sure, the simplest and most general of a group of adjectives indicating full belief and trust that something is true, expresses the mere absence of doubt. Certain suggests that there are definite reasons that have freed one from doubt. Confident emphasizes the strength of the belief or the certainty of expectation felt. Positive implies emphatic certainty, which may even become overconfidence or dogmatism. 

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

"I was looking at that camera the whole night to make sure it was working," said Natalie Orrantia, one of the students involved in the discovery.

From Science Daily • Apr. 4, 2026

I’m not sure we should reject the impulse to explore extreme ideas to stop global heating, since the current consensus seems to be doing next to nothing.

From Salon • Apr. 4, 2026

And while AI-based shopping is still a niche practice, some retailers are giving their inventory descriptions another look to make sure their products are AI-ready if and when more shoppers arrive.

From The Wall Street Journal • Apr. 4, 2026

He added: "I'm quite sure we'll never be sharing those details."

From BBC • Apr. 3, 2026

And I know for sure that I do mean it: forever forever.

From "Red Flags and Butterflies" by Sheryl Azzam

From Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.