汉语翻译：
n. 乐观主义, 乐观, 乐天
【医】 乐观主义, 乐观英语解释：
名词 optimism:

the optimistic feeling that all is going to turn out well

a general disposition to expect the best in all things

例句：

Her mood varied from optimism to extreme depression.她的情绪由乐观一变而为极度消沉。

He swings from wild optimism to total despair.他由极其乐观一变而为完全绝望。

At the outset of her career she was full of optimism but not now.她事业伊始十分乐观，但现在已今非昔比了。

They professed optimism about the outcome.他们对结果表示乐观。

I would caution against undue optimism.我奉劝不要过於乐观。

Pessimism, when you get used to it, is just as agreeable as optimism.悲观主义者，当你习惯它之后，就和乐观主义者一样令人惬意了。

详细解释：
op.ti.mism
n.（名词）
A tendency to expect the best possible outcome or dwell on the most hopeful aspects of a situation:
乐观主义，乐观：期待一切都朝着好的方向发展或总是考虑事情最有利的方面的一种倾向：
例句：
.There is a touch of optimism in every worry about one`s own moral cleanliness.(Victoria Ocampo)
.在对自身道德纯净度的每次焦虑中，都存在一种乐观因素.(维多利亚·奥卡姆波)
Philosophy
【哲学】
The doctrine, asserted by Leibnitz, that this world is the best of all possible worlds.
尽善尽美论：由莱布尼兹创建的一种理论，认为这个世界是尽善尽美的
The belief that the universe is improving and that good will ultimately triumph over evil.
乐观论：认为世界是不断发展完善的，善最终必战胜恶的理论
来源：
French optimisme
法语 optimisme
from New Latin optimum [the greatest good] * see optimum
源自 现代拉丁语 optimum [最有利的一面] *参见 optimum

optimism