grammaticality - Identifying the class of this word

I'm reading the Wikipedia page on garden-path sentences. One example is:

The government plans to raise taxes were defeated.

What class of word is government in this sentence?

I read this sentence as having the subject noun "plans". "Government" describes the noun, which would make it an adjective. I thought that the adjective form of "government" was "governmental".

The sentence may imply ownership of the plans by the government (as opposed to describing the type of plans, distinct from council plans or building plans). In this case, I would have written it as "the government's plans...".

Either way, I'm unsure how to determine whether the given sentence is grammatically correct. Assuming it is, what class of word is government?

[Slightly separate question: what's the correct term for "the class of word", such as 'adjective', 'noun'? Had issues phrasing my question without knowing this.]