Many words can be categorized into two or more parts of speech. For example, ‘fall’ is both a verb and a noun. In, ‘He fell to his knees’, it is a verb. But, in ‘A heavy fall of rain’, it is a noun.
The two articles are [a, an] and the. ‘A’ is sometimes classified as a noun in a dictionary. But, in a phrase like ‘kind of a computer’ [here, it means that there is one computer with many similar models] it modifies the noun ‘computer’ and so it can be classified as an adjective since adjectives modify nouns. [compare ‘the computer’]. But, in the phrase, ‘a kind of computer’ [here, it means a machine which is similar to a computer] it modifies the adjective ‘kind’ and so it is an adverb since adverbs modify adjectives.
So, articles can be classified as adverbs and adjectives, too. [?].