用作定语
▲～+n.
He is an optimistic person.他是位乐观主义者。
He is an optimistic young fellow.他是位乐观的年轻人。
用作表语
▲S+be+～+prep.-phrase
She is not optimistic about the future.她对未来并不乐观。
▲S+be+～+that-clause
The experts are optimistic that we will succeed.那些专家对我们的成功抱乐观态度。