1. 自信;胸有成竹
Someone who has self-assurance shows confidence in the things that they say and do because they are sure of their abilities.

1. freedom from doubt
belief in yourself and your abilities

e.g. his assurance in his superiority did not make him popular
after that failure he lost his confidence
she spoke with authority

Synonym: assuranceconfidenceself-confidenceauthoritysureness