The ancient castle's fortifications were built to defend against enemy attacks.

fortifications 是名词 fortification 的复数形式。fortification 由词根 fort（来自拉丁语 fortis，意为"强壮的"）和名词后缀 -ification（表示"使...化"的过程）组成，字面意思是"使变得坚固的过程或结果"。 在军事术语中，fortifications 特指"防御工事"，包括城墙、堡垒等用于抵御敌人进攻的建筑结构。