Her restlessness kept her from staying quiet during the meeting.

restlessness 是由形容词 restless（不安的、焦躁的）加上名词后缀 -ness 构成的名词。restless 由前缀 re-（表示"反复"）和词根 -st（站立）组成，字面意思是"反复站立"，引申为"坐立不安"。 -ness 是常见的名词后缀，表示某种状态或性质。restlessness 指"不安、焦躁"的心理状态。