the quality of being full of hope and emphasizing the good parts of a situation, or a belief that something good will happen

There was a note of optimism in his voice as he spoke about the company's future. 谈到公司的未来，他语气里带着乐观情绪。

They had cause/grounds/reason for cautious optimism about an improvement in her medical condition. 他们对她的病情持谨慎的乐观态度。