The high fever caused the old man's delirium, and he couldn't recognize his own room.

delirium 是名词，来自拉丁语，由前缀 de-（表示"偏离"）和词根 lira（"犁沟、轨道"）组成，字面意思是"偏离轨道"。在医学上指"谵妄"，是一种因高热、中毒等导致的精神错乱状态，表现为意识模糊、幻觉和认知障碍。