Predicate Indefinite Article

English Grammar;

This page is intended to describe one of the usages of the indefinite article where an indefinite article before a singular countable noun has a function to express the general meaning of this noun, not a particular case: a plural countable noun without article, also, an uncountable noun without article can be treated in the same manner.

My favorite animal is a dog.

This sentence is correct, though many other European languages would prefer definite article to indefinite article before “dog”, otherwise plural.

My favorite animal is the dog.

My favorite animal is dogs.

This usage of singular indefinite article in English seems exceptional and worth studying its conceptual structure.

When you look up a word in a dictionary, the definition is written in a conventional way such as;

A crow is a large black bird which makes a loud harsh noise…

A crow is a type of bird that is generally black in colour and…

This indefinite article is usually considered as a kind, a sort, a group, etc. For “a horse is a mammal” or “horses are a mammal”, a mammal means a sub-set of the set “the mammals”.

But, here, we are going to be thinking much differently.

What is an indefinite article in English grammar?

A determiner (a and an in English) that introduces a noun phrase and implies that the thing referred to is non-specific (as in she bought me a book; government is an art; he went to a public school). Typically, the indefinite article is used to introduce new concepts into a discourse. Compare with definite article. Oxford Dictionary

Non-specificity of indefinite article can take an interesting logical turn.

A crow is a large black bird which…

If there is a crow, this crow is necessarily a large black bird which…

Here, a crow means any crow, which is arbitrary chosen, i. e., every crow. This Venn diagram shows a crow that is arbitrary chosen is necessarily a bird. It is a very logical expression to say that the crows are birds.

Predicate Indefinite Article

“Predicate” is a mention to define something is something. Instead of saying, the crows are birds, a predicate indefinite article can mention the same thing in a mild expression; a crow is a bird. It means; if there is a crow, it is logically a bird.

In this Venn diagram, the birds make a “set” and the crows make a smaller set, “sub-set”.

Two sets can be equal, too, such as; the corvus are the crows, or, a corvus is a crow.

Diamonds Are a Girl’s Best Friend

There is no plural form for indefinite article.

Diamonds are a girl’s best friend.

The best friend of a girl is diamonds.

The two sets are equal.

If there are diamonds, they are necessarily the best friends of a girl.

If there is a girl, her best friend is necessarily diamonds.

“Diamonds” means any diamond, and “a girl” means any girl: the non-specificity of an indefinite article generalize the following noun. That is better than a heavy phrase, such as; the diamonds are the best friends of the girls.

Water is H₂O

The word “water” is an uncountable noun, therefore you cannot put an indefinite article before it, but here it should not be considered as all the water in the universe or water in an abstract meaning, but a certain quantity of water, a portion of water. It does not have an indefinite article, only because it is an uncountable noun. If there is a portion of water, it is necessarily H₂O, means, any arbitrary chosen portion of water is H₂O.

Predicate Indefinite Article