Learner's definition of OPTIMISM
a feeling or belief that good things will happen in the future
a feeling or belief that what you hope for will happen
Both of them expressed optimism about the future of the town.
The early sales reports are cause/reason/grounds for optimism.
Most of us reacted to the news with cautious/guarded optimism. [=a feeling that something good may happen but will not definitely happen]
There is growing optimism that the problem can be corrected.
He maintains a sense of optimism, despite all that has happened.