[Grammar] the cow or a cow

[Abhish]

Good Morning,
I have a doubt.There are two sentences
1 A cow is a useful animal.
2 A cow is a useful animal for the farmers of India.
3 The cow is a useful animal.
My teacher told me that first one and second one is correct but I have gone through many English sites online and according to them,the third one is correct.
I have even found many matching sentences
the wolf is not really a dangerous animal or wolves are not really a dangerous animal.Here,the wolf represents the class.

But,in a grammar book by Martin Hewings,I found that when we define something,we generally use a/an.But in the 1 and 2 sentences,we are not defining something.
4 Cow is an animal.
Here,we are defining cow that is it is an animal.
Can you please explain which of the sentences are right and tell me the logic/rule behind it.
Thanks

 

[SoothingDave]

I would use "the cow," since you are talking about the species of animal in general and not just one particular cow. Also, you are not recommending this for one particular farmer, either.

 

[TheParser]

NOT A TEACHER


Good morning, Abhish:


I am delighted to tell you what two scholars * say.

1. The cow is a useful animal.

a. This is "formal usage." (classes of humans, animals, etc.)

2. Cows are useful animals.

a. This is "slightly less formal."

3. A cow is a useful animal.

a. This is "the most concrete and colloquial way of expressing a generality."

*****

NOTES:

1. The two scholars did not use "cow" in their examples. I have based my examples on the information that they

have given.

2. * Marianne Celce-Murcia and Diane Larsen-Freeman, The Grammar Book (1983), pages 180 - 181.


HAVE A NICE DAY!