Why an article is not used before but

"But" is a coordinating conjunction that joins two independent clauses. An article is not used before "but" because it is not a noun. In English, articles are used before nouns to indicate whether the noun is specific or general. For example, we use the definite article "the" to refer to a specific noun, as in "the man," and the indefinite article "a" or "an" to refer to a general noun, as in "a man." However, "but" is not a noun, so it does not require an article.