She is very perceptive and quickly spotted the subtle differences in the photos.

perceptive 是由动词 perceive（感知、察觉）加上形容词后缀 -tive 构成的形容词，表示"有洞察力的、敏锐的"。perceive 本身由前缀 per-（完全）和词根 ceive（拿、取）组成，字面意思是"完全获取（信息）"。