So what part of speech is the above?
Is it considered to be a compound noun, like a bus station? If so, what the part of speech (in Japanese) to represent such constructions?
延命 here acts like a descriptive adjective of 処置 yet they are both listed as nouns. There is no entry for 延命処置 as one word. Yet they go together here, they’re not meant to be interpreted as two unrelated nouns.
I think there’s a word for this in Japanese grammar and I’d like to know what it is.
Thank you.
Is it considered to be a compound noun, like a bus station?
Yes. It's not a suru-verb because we say 延命処置を行う but not 延命処置する.
If so, what the part of speech (in Japanese) to represent such constructions?
"Compound noun" is 複合名詞 in Japanese. You can find discussions about this in the following questions:
There is no entry for 延命処置 as one word.
It's a compound noun, so that's understandable. Many common compound nouns are so straightforward that they are not listed in dictionaries. For example, there is nothing surprising in the meaning of スマホケース ("smartphone case"), シーフードピザ ("seafood pizza") or タクシー運転手 ("taxi driver"), and no one wants to look them up in the dictionary. Still, there may be entries for them in Wikipedia if the combination is important.
