There was a note of optimism in his voice as he spoke about the company's future.

optimism 是由词根 optim（表示"最好的"）加上后缀 -ism（表示"主义、态度"）构成的名词，字面意思是"认为事情会向最好的方向发展"，即"乐观主义"或"乐观态度"。