grammar - Why is there no plural indefinite article?

The takes either a singular or a plural subject. A/an only takes the singular.

When we pluralize a noun preceded by an indefinite article, we simply drop the article (sometimes replacing it with some). Why is this?

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3 years later:

Whilst on a separate goose-chase, I came across Greg Carlson's 1977 paper A Unified Analysis of the English Bare Plural, which addresses this issue in refreshing detail. It does not answer my question etymologically, but it substantiates the premise that the so-called null determiner is ambiguous:

ABSTRACT. It is argued that the English ‘bare plural’ (an NP with plural head that lacks a
determiner), in spite of its apparently diverse possibilities of interpretation, is optimally represented in the grammar as a unified phenomenon. The chief distinction to be dealt with is that between the ‘generic’ use of the bare plural (as in ‘Dogs bark’) and its existential or ‘indefinite plural’ use (as in ‘He threw oranges at Alice’). ‘Ihe difference between these uses is not to be accounted for by an ambiguity in the NP itself, but rather by explicating how the context of the sentence acts on the bare plural to give rise to this distinction. A brief analysis is sketched in which bare plurals are treated in all instances as proper names of kinds of things. A subsidiary argument is that the null determiner is not to be regarded as the plural of the indefinite article a.

The primary distinction is summed up in these examples:

Weeds grow refers to all weeds, or weeds in general. It is not equivalent to Some weeds grow.

Weeds grow in my garden refers to some weeds, and is equivalent to Some weeds grow in my garden.

I understand that context is often sufficient to determine the scope of the noun without a plural indefinite article¹ - but that applies to the singular indefinite article a/an as well. In fact, it seems that a/an is even more redundant, since both Dog barks and Dog barks in my garden are equally indefinite, not generic.

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¹Carlson 2001 is further germane analysis. In here, he gives examples of sentences for which context is not sufficient to determine the scope of the null determiner. For instance, I only excluded old ladies can mean I excluded all old ladies (generic), or that all those whom I excluded happen to have been old ladies (indefinite - some old ladies may have gotten in after all).

Answer

In most languages indefinite articles stem from that language's word for one. For instance in French un, or in German ein, In Italian and Spanish uno or in Portuguese um.

English is no exception: an was derived from one. Note that an was the original indefinite article; the shorter a came later when the final "n" was dropped before consonants.

In some of the languages I mentioned above, the plural form of the indefinite articles is simply formed by applying the noun plural inflection: unos/unas or uns/umas.

In others, such as German and Italian, there is no plural form to the indefinite article. Italian use the partitive article degli/delle as a substitute and this is probably also the origin of the French plural form des.

For some reason English did not go through this last step either. To understand why we need to go back to the way Old English solved the problem.

In Old English adjectives have a different declension depending on whether the noun they qualify is determined or not.

"The glad man" reads

se glæd guma

whereas, "a happy man" is:

glæda guma

As one can see, only the adjective changes.
For one given adjective, you could therefore have different inflections depending on:
- the noun gender (masculine, feminine, neuter)
- the noun being singular or plural
- the four cases (nominative, accusative, genitive, dative)
- whether the reference is definite or indefinite.
So that the same adjective would have to follow either the "definite" declension or one of three "indefinite" declensions.

þa glædan guman

Edit

The theory I'm trying to check (community please feel free to edit) is that in various languages (Icelandic for a language very close to Old English or Romanian) the article is added as a suffix to the noun. Then it often "detaches" and passes in front of the noun. Icelandic is half way through for the definite article in that matter.

As for the Old English indefinite article, my conjecture is that the process never went through for a number of possible reasons:
- The "loss of inflection" of early Middle English won the race
- The plural of "an" was not easy to evolve at that time (the Romance "-s" plural had not imposed itself yet).

But the need is still there, just as in any other language where a specific word emerged for the plural indefinite article. This gap is filled by placeholders such as some or a number of.

Most linguist agree that Proto Indo European did not use articles.
Latin does not have any kind of article, and Ancient Greek arguably had no indefinite article either - it was using something very much like present-day English some (τις - "a certain"). And I believe that Old German did not have any article either.

It is a very remarkable fact that articles appeared in many modern Indo European languages in a largely mutually independent yet very similar manner. My feeling is that their emergence compensates for the gradual loss of inflection in these languages. But then present-day German is a powerful counterexample...