名词作表语是用来说明主语的身份、性质、品性、特征和状态的词或从句。它们通常位于系动词（如be动词）之后。以下是一些名词作表语的例子：
He is a teacher.
I am a student.
The human nose is an underrated tool.
Africa is a big continent.
My brother is a teacher.
Her goal is to become a doctor.
My best friend is Mary.
The problem is that we don't have enough money.
这些例子展示了名词在句子中作为表语的不同用法，它们帮助描述了主语的具体情况或状态。