Parts of speech in a language

The fundamental problem with the question is the assumption that a language 'has' some sort of fixed categories of words joined together by common properties. It is understandable because typical language pedagogy makes it seem that 'parts of speech' are some sort of natural types.

But in fact, nothing could be further from how languages operate. These are the key things to know about 'parts of speech' or 'word types'.

1. There is no definitive list of word types for any given language. Any list will be the result of tradition and theoretical assumptions made by the person compiling a particular grammar. In English grammars, you can find lists of anywhere between 8 and 11. In other languages, you will find wildly different lists.

2. The criteria for including a word in a particular category combine function, meaning, morphology and syntax in various inconsistent ways. This makes it hard to come up with many meaningful crosslinguistic universals.

3. Word categories do not have clear boundaries. There are many edge cases and possible disputes. Some linguists have talked about things like 'nouniness' to indicate the problem.

4. The only true universally recognized word types that are identified in all languages are nouns and verbs with a strong case being made for adjectives. But even this does not always mean that a word that is a noun in one language cannot be a verb in another and vice versa. In effect, word types are very much specific to each language.

5. Despite their problematic nature, word types (parts of speech) are very useful when dealing with text. For instance, in natural language processing, language teaching, corpus linguistics, etc. But it is important not to treat them as fixed and immutable. They're just helpful heuristic devices.