According to Wikipedia (disclaimer: of course I realize that Wikipedia should not be regarded as an absolute authority, but I generally consider it to be a fairly accurate and reliable resource):

Articles specify the grammatical definiteness of the noun . . .

I guess I can understand how the words the, an, and a fit this description. But what about words such as this, that, those, etc.? It seems these serve essentially the same function (specifying definiteness), but unless I'm mistaken, they are categorized as demonstrative adjectives.

I find this particularly puzzling in light of the following two excerpts from Wikipedia:

Every noun must be accompanied by the article, if any, corresponding to its definiteness, and the lack of an article (considered a zero article) itself specifies a certain definiteness.

[. . .]

In languages having a definite article, the lack of an article specifically indicates that the noun is indefinite.

It seems to me that, in light of the above two statements, an expression such as "those boots" should somehow be considered indefinite (since there is no article), but isn't this absurd?