His indifference to the suffering of others was shocking.

indifference 是名词，由前缀 in-（表示"不"）和 difference（"差异、区别"）组成，字面意思是"没有区别对待"。引申为"冷漠、不关心"的意思，指对某事缺乏兴趣或关注的态度。