assured
Confident and sure, without doubt or worry.
Assured means confident and certain, without doubt or worry. When someone speaks in an assured voice, they sound calm and convinced of what they're saying. An assured athlete steps onto the field knowing they've practiced enough to perform well.
The word describes a quiet, steady kind of confidence. It's not showing off or boasting: it's the feeling you get when you've studied hard for a test and walk into class knowing you're ready. An assured manner comes from preparation and experience. A pilot flying through turbulence with an assured touch at the controls can make passengers feel safe.
Assured can also mean guaranteed or certain to happen. If your teacher says your field trip is assured, it's definitely going to happen. When success seems assured, it means the outcome looks certain, though smart people know that nothing is ever completely guaranteed until it actually happens.
Related words include self-assured (confident in yourself) and assurance (confidence or a promise that something will happen). Someone with self-assurance doesn't need constant praise or approval because they trust their own abilities.