"Types of" followed by singular or plural? [duplicate]

Solution 1:

I think your essential concern is about countable vs. uncountable nouns. Countable nouns can be singular or plural; uncountable nouns are singular. Some words can be both, in different meanings.

Take a look at this example discussing countable and uncountable nouns:

The coffees I prefer are Arabica and Brazilian. (Here coffees refers to different types of coffee)

You could write, "The types of coffee I prefer are Arabica and Brazilian."

So with your example:

The rocks I like are basalt and granite. [Rocks are countable]

The types of rock I like are basalt and granite. [Rock is uncountable]

When rock is taking on the uncountable meaning, it's not one rock - it's the idea of rock, the general concept. The only senses in which this is familiar to me are the "solid mineral" one and rock as in "rock music," where you might say, "The types of rock I like are grunge and punk."

Contrast the other part of your example:

The sentences I like are about geology. [Sentences are countable]

The types of sentences I like are about geology. [Sentences are still countable]

Sentences don't have an uncountable meaning:

*The types of sentence I like are about geology. [Ungrammatical for most speakers, I think]

Solution 2:

Here's a rule of thumb with which to decide the correct usage in any given case.

Turn the phrase around:

I like all kinds of music = I like music of all kinds

I like all kinds of apple ≠ I like apple of all kinds

I like all kinds of apples = I like apples of all kinds

And so on.

Solution 3:

Good question. There may not be a hard and fast rule other than what sounds better, and I probably won't explain this right, but "types of [singular]" is generally a label that implies a division within a general class noun, while "types of [plural]" is generally a label that implies a grouping of individual items.

"Types of metal", for instance, indicates that you are attempting to discern between various varieties of materials that, in general, are referred to or described as "metal". These types, possibly referred to by their elemental or common names (lithium, iron, magnesium, and alloys like steel), are "metals", plural. To say "types of metals" indicates an attempt to regroup these individual variants under headings more general than their basic names, but less generic than the overall concept "metal". To illustrate: "Gold is a type of metal, belonging to the transition metals". Gold is identified in the singular as a variant of the basic class of metal, then grouped with other types of metal to form a type of metals.

Confused yet? Again, probably no hard and fast rule, but after some thought, this was the best I could come up with.