1. to display or express confidence and assurance about something; to make evident one's conviction or sureness about a matter
She showed certainty in her decision despite the criticism.
Ela demonstrou certeza em sua decisão apesar das críticas.
2. to exhibit clear, unmistakable signs of being sure or confident
His steady voice showed certainty about the project's success.
Sua voz firme mostrava certeza sobre o sucesso do projeto.