Kind of/sort of/type of+ noun

[kachibi]

I always come across this problem: not knowing if the countable noun after kind of/sort of/type of must be singular or plural. I read a number of grammar sites and I have the following conclusion. Yet, I still want some standard grammar teachers to confirm it:

Correct:
1) An eagle is a kind of bird. (singular+ no article)
2) There are many kinds of butterflies. (plural)

Incorrect:
1) An eagle is a kind of birds. (when using "a kind", the subsequent noun must be singular to echo it.)
2) There are many kinds of butterfly. ("butterfly", unlike "water", is a countable noun. And when using "many kinds", it has to be echoed by "butterflies".)

Am I correct?

[emsr2d2]

I always come across this problem: not knowing if the countable noun after kind of/sort of/type of must be singular or plural. I read a number of grammar sites and I have the following conclusion. Yet, I still want some standard grammar teachers to confirm it:

Correct:
1) An eagle is a kind of bird. (singular+ no article)
2) There are many kinds of butterflies. (plural)

Incorrect:
1) An eagle is a kind of birds. (when using "a kind", the subsequent noun must be singular to echo it.)
2) There are many kinds of butterfly. ("butterfly", unlike "water", is a countable noun. And when using "many kinds", it has to be echoed by "butterflies".)

Am I correct?

I would use the singular in both cases.

An eagle is a kind of bird.
There are many kinds of butterfly.

A Red Admiral is a kind of butterfly.
A Cabbage White is a kind of butterly.
These are two kinds of butterfly.

To be accurate, I think they are actually "species" of butterfly, not "kinds".

[kachibi]

Thanks, so you mean the noun must be singular without any article under all circumstances right?

Then why people's answers are contradictary for this kind of case? Some say plural nouns are correct, some say "a kind of birds" is correct because you want to mention ONE KIND of MANY DIFFERENT BIRD KINDS.

Or there are actually no reasons but it is a rigid grammar rule?

[emsr2d2]

Thanks, so you mean the noun must be singular without any article under all circumstances right?

Then why people's answers are contradictary for this kind of case? Some say plural nouns are correct, some say "a kind of birds" is correct because you want to mention ONE KIND of MANY DIFFERENT BIRD KINDS.

Or there are actually no reasons but it is a rigid grammar rule?

I don't know who has told you that "a kind of birds" is correct but I can't think of a single circumstance where that would be acceptable.

[kachibi]

thanks so much=]

[philo2009]

I always come across this problem: not knowing if the countable noun after kind of/sort of/type of must be singular or plural. I read a number of grammar sites and I have the following conclusion. Yet, I still want some standard grammar teachers to confirm it:

Correct:
A1) An eagle is a kind of bird. (singular+ no article)
A2) There are many kinds of butterflies. (plural)

Incorrect:
B1) An eagle is a kind of birds. (when using "a kind", the subsequent noun must be singular to echo it.)
B2) There are many kinds of butterfly. ("butterfly", unlike "water", is a countable noun. And when using "many kinds", it has to be echoed by "butterflies".)

Am I correct?

B2 is quite correct, though rather formal. A2 would be the normal conversational equivalent.

B1 is incorrect. However, this combination of singular classifier and plural object noun is informally acceptable in interrogative phrases, e.g.

What kind of people applied for the job?

(= formal What kind(s) of person...)

[kachibi]

Got it got it~
Thanks.
So now I understand it's the matter of whether it is formal or not.