optimism n. 樂觀，樂觀主義
例句：At the outset of his career he was full of optimism but not now.
他事業伊始十分樂觀，但現在已今非昔比了。

pessimism n. 悲觀，悲觀主義
例句：Nicholas never gave himself up to pessimism in spite of difficulties.
盡管遇到困難，但是尼古拉斯從沒有消極悲觀過。

pessimistic adj. 悲觀的，厭世的
例句：She tried to shut all pessimistic thoughts out of his mind.
他努力從頭腦中排除一切悲觀的想法。

optimistic adj. 樂觀的
例句：He was always optimistic, even when things were at their worst.
他即使在最糟糕的時候也總是非常樂觀。

optimum n. 最適宜 adj. 最適宜的
例句：The market offer optimum condition for sale.
市場為銷售提供了最佳條件。