optimism n. 乐观，乐观主义
例句：At the outset of his career he was full of optimism but not now.
pessimism n. 悲观，悲观主义
例句：Nicholas never gave himself up to pessimism in spite of difficulties.
pessimistic adj. 悲观的，厌世的
例句：She tried to shut all pessimistic thoughts out of his mind.
optimistic adj. 乐观的
例句：He was always optimistic, even when things were at their worst.
optimum n. 最适宜 adj. 最适宜的
例句：The market offer optimum condition for sale.