optimism n. 乐观，乐观主义
例句：At the outset of his career he was full of optimism but not now.
他事业伊始十分乐观，但现在已今非昔比了。

pessimism n. 悲观，悲观主义
例句：Nicholas never gave himself up to pessimism in spite of difficulties.
尽管遇到困难，但是尼古拉斯从没有消极悲观过。

pessimistic adj. 悲观的，厌世的
例句：She tried to shut all pessimistic thoughts out of his mind.
他努力从头脑中排除一切悲观的想法。

optimistic adj. 乐观的
例句：He was always optimistic, even when things were at their worst.
他即使在最糟糕的时候也总是非常乐观。

optimum n. 最适宜 adj. 最适宜的
例句：The market offer optimum condition for sale.
市场为销售提供了最佳条件。