Lexical categories (
link) differ from language to language and within a language. It's a matter of linguistic analysis not some actual property of the words. The trad eight for English are adapted from the Graeco-Roman grammatical tradition, which tended to categorize by endings, e.g., nouns substantive and adjective share the same set of endings. Modern English grammatical theory has a slightly different take, e.g., the articles not being their own category but subsumed under determiners, etc. Reading the Wikipedia article linked to above is a good start, and there are further references at the bottom of the page there. Modern grammatical theory tends to classify words by what slots they fill in a sentence, i.e., by syntactic function.
As for other languages, I don't know much about Chinese grammatical theory and its history, but I would hazard to say it is different from Indo-European traditions. A word in Chinese can be used as a noun, adjective, verb, what have you. It's more about where it occurs in the sentence, Chinese not having much inflectional morphology, if any at all.
