They had to overcome many obstacles to achieve their goal.

obstacles 是名词 obstacle 的复数形式，obstacle 由前缀 ob-（表示"反对、对抗"）和词根 stacle（来自拉丁语 stare，意为"站立"）组成，字面意思是"站在对立面的东西"，引申为"障碍、阻碍"。