Her memory has noticeably deteriorated since she got ill.

deteriorated 是动词 deteriorate 的过去分词形式。deteriorate 由前缀 de-（表示"向下、变坏"）和拉丁词根 ter（表示"磨损"）以及动词后缀 -ate 组成，字面意思是"逐渐磨损变坏"，引申为"恶化、衰退"的意思。