The cat seems unaffectionate and never approaches people on its own.

unaffectionate 是由前缀 un-（表示"不、非"）和形容词 affectionate（"深情的、充满爱的"）组成的复合词。affectionate 本身来自名词 affection（"感情、喜爱"）加上形容词后缀 -ate。因此 unaffectionate 整体意思是"不亲热的、冷淡的"。