"These are THE three different types of services". Is this correct?

Question

I was reading Google's Android documentation and came across with this sentence. Link: https://developer.android.com/guide/components/services

There is written like this: "These are the three different types of services:" and it counts the services. To me that "the" article before "three" sounded awkward and I have never seen that usage before. Is it correct? If so, what made them put the article in that sentence?

What is the difference between "These are three different types of services:" with "These are the three different types of services:"?

Answer 1

Adding the definite article before a number indicates that the list is complete. In the example provided "These are three different types of services" indicates that only three are listed, but more are possible; "These are the three different types of services" indicates that the list contains all possible services, no other items are available.

Answer 2

These are three different types of services.

Since there is no definite article, it is implied that there are more than three types of services, and the sentence happens to refer to these three. Similarly, someone could say, "Apples, oranges, and bananas are three different types of fruit that we sell." We can assume that there are more types of fruit that they sell, while the sentence happens to refer to these three particularly examples.

These are the three different types of service.

With the definite article the, we can assume that these three types of services are the only types of services, or at least the only types of services that are relevant. The definite article indicates that this group is the one complete set, rather than simply one possible group of three services out of many possible groups. Similarly, someone could say, "Apples, oranges, and bananas are the three different types of fruit that we sell." There may be many other types of fruit in the world, but we know that these people sell only apples, oranges, and bananas.