Not a natlang, but Alurhsa has this.  Sálek (book), sálekó (books, as in 
more than one book), sálekár (books that form a collection).

Same with tree: bhelk, bhelkó (more than one tree), bhelkár (trees in a 
stand, a collection of trees, a wood).

Interestingly the -ár words are treated as singular, not plural, in 
Alurhsa as far as verb/pronoun agreement.



On 11/04/2010 05:34 PM, Philip Newton wrote:
> On Thu, Nov 4, 2010 at 18:49, Gary Shannon<[log in to unmask]>  wrote:
>> My 30-day conlang seems to be developing two different kinds of
>> plural. The first is the usual "more than one" and the second has a
>> sort of mass noun type implication and is grammatically like a
>> singular. For example "hair" which in the singular means a single
>> strand of hair, in the plural_1 means several strands of hair, and in
>> plural_2 means "hair" as a mass substance. So you might say "Many
>> hair-Plural_1", but "Much hair-Plural_2".
>>
>> Another example might be the word for "mountain" which in plural_1
>> means several mountains, but in plural_2 might mean "mountain range".
>> Same with tree/trees/forest, plank/planks/lumber, or "1 item of
>> trash"/"several items of trash"/"lots of trash (mass)".
>>
>> Does anything like that exist in any natlang? Does that sound reasonable?
> I think Romansh has something, if not like that, then at least
> similar: some nouns form not only a regular plural but also a form in
> -a which is morphologically feminine singular and which is a
> collective, I think - so for "il pez" (peak) you have not only "ils
> pezs" (peaks) but also "la pezza" which is a sort of collective
> "mountain range" or something like that. Or "il crap" (stone) gives
> "ils craps" (stones) and "la crappa" (a mass of stone, a rocky area).
>
> Cheers,
> Philip