不一定是冠词，如果有数量，或者表示指代谁的的时候就不需要。

例句如下：

This is the dining hall. 冠词the表特指。

This is an dining hall. 冠词an表数量。

We have two buildings in the school. 数词two

How many libraries are there in your university? 数量疑问词How many

Is this your apartment? 物主代词your你的

希望可以帮到你。欢迎追问。