sure, certain, positive, cocksure mean having no doubt or uncertainty. sure usually stresses the subjective or intuitive feeling of assurance. certain may apply to a basing of a conclusion or …

POSITIVE definition: 1. full of hope and confidence, or giving cause for hope and confidence: 2. certain and without…. Learn more.

1. characterized by or expressing certainty or affirmation: a positive answer. 2. composed of or possessing actual or specific qualities; real: a positive benefit. 3. tending to emphasize what is good …

showing or expressing approval or agreement; favorable: a positive reaction to the speech. consisting in or characterized by the presence or possession of distinguishing or marked qualities or features …

If you are positive, you are hopeful and confident, and think of the good aspects of a situation rather than the bad ones.

There are 39 meanings listed in OED's entry for the word positive, seven of which are labelled obsolete. See ‘Meaning & use’ for definitions, usage, and quotation evidence.

In English, the term 'positive' acquired the connotation of being characterized by optimism, favorability, or a constructive nature, reflecting an affirmative and confident stance.