1. A dog is a faithful animal.

2. A dog is one faithful animal.
3. A dog is any faithful animal.
4. A dog is every faithful animal.
5. A faithful animal is a dog.
6. One faithful animal is a dog.
7. One faithful animal is one dog.
8. One faithful animal is any dog.
9. Any faithful animal is any dog.
---------------------------------------
Does #1 mean #2? Does 'a' mean 'one'?
Is 'a faithful animal' is a generic noun phrase? Then, does #1 mean #3 or #4? Can we use such expressions?
What about #5? Does #5 mean #7 or #9 or any other thing?

Yes, “a” usually means one, but speaking about dogs in general, I’d use 1 and 5, and maybe 6. The others aren’t quite right.

Let's break down the sentences and analyze their meanings:

1. A dog is a faithful animal.
- This sentence means that dogs, in general, are faithful animals.
- In this context, "a" is a generic article used to refer to a type or category of animals (dogs) without specifying a particular one.
- This sentence does not mean the same as sentence #2.

2. A dog is one faithful animal.
- This sentence means that among various faithful animals, a dog is one of them.
- Here, "one" is used to emphasize that a dog is a specific instance of a faithful animal.
- Sentence #2 does not have the same meaning as sentence #1.

3. A dog is any faithful animal.
- This sentence means that any animal that is faithful can be referred to as a dog.
- Here, "any" is used to indicate that as long as an animal is faithful, it can be categorized as a dog.
- Sentence #3 does not have the same meaning as sentence #1 or #2.

4. A dog is every faithful animal.
- This sentence means that every single faithful animal is categorized as a dog.
- Here, "every" is used to suggest that there are no faithful animals that do not fall into the category of a dog.
- Sentence #4 does not have the same meaning as sentence #1, #2, or #3.

5. A faithful animal is a dog.
- This sentence means that any animal that is faithful can be called a dog.
- It implies that the quality of faithfulness defines what is meant by a dog.
- Sentence #5 does not have the same meaning as sentence #7 or #9.

6. One faithful animal is a dog.
- This sentence means that among various faithful animals, there is one (not more than one) that is specifically a dog.
- It emphasizes that out of all the faithful animals, there is a single dog.
- Sentence #6 does not have the same meaning as sentence #5, #7, or #9.

7. One faithful animal is one dog.
- This sentence means that there is an animal that is faithful and that animal is specifically a dog.
- It emphasizes that there is only one animal and it happens to be a dog.
- Sentence #7 does not have the same meaning as sentence #5, #6, or #9.

8. One faithful animal is any dog.
- This sentence means that there is a single animal that is faithful and it can be any dog.
- It suggests that the specific dog does not matter as long as it is faithful.
- Sentence #8 does not have the same meaning as sentence #5, #6, or #9.

9. Any faithful animal is any dog.
- This sentence means that any animal that is faithful can be classified as any dog.
- It indicates that as long as the animal is faithful, it can be categorized as any specific dog.
- Sentence #9 does not have the same meaning as sentence #5, #6, or #7.

In summary, the statements you provided have different meanings and interpretations. They do not all mean the same thing, and they use different wording and emphasis to convey their ideas.