The doctors are pessimistic about his chances of recovery.

pessimistic 是形容词，由名词 pessimism（悲观主义）派生而来，词根 pessi- 来自拉丁语 pessimus（最坏的），后缀 -istic 表示"具有...特性的"。这个词形容对事情持消极、不乐观的看法。