X は Y です is Y a noun, adjective, or neither?

I’m coming to realize my sense of adjectives vs nouns is a bit fast and loose, because often in English the noun and adjective form of a word is the same. For example, black is both an adjective and a noun. Where in Japanese the noun form is 黒 and the i-adjective form is 黒い

The black dog => black is an adjective.

The dog is black => Not sure is black is an adjective or noun here. Not the primary question, but would be curious to know!

At any rate, would the correct translation be

or more generally, can Y be a noun, i-adjective, or neither? Thanks!

In your example, it has to be the adjective. Unless the dog is literally not a dog and is in fact a color, black. I guess you could imagine that being poetic somehow.

An example of using the noun would be

好きな色はなんですか What is your favorite color?
(好きな色は)黒です (As for my favorite color) It’s black

Since you’re asking what “Y” could be in general, it could also be a な adjective.


I see, so it’s 犬は黒いです then?

Also, would it be a stretch to say that anything of the form X wa Y desu, where Y is an adjective, the desu basically means =?

Doesn’t です always mean roughly “=”? (Since it pretty much means “is/am”)

In sentences of the form X wa Y desu, where Y is an adjective, the desu is just a politeness indicator. So 犬は黒いです is a more polite way of saying 犬は黒い


Yeah, です has no meaning after an い adjective other than politeness.

It is not a copula. Because an い adjective cannot take a copula.


You can just say 黒い犬 too instead of using the pattern. But, you probably know that and just wanted to know about the pattern, thought I’d mention it anyways.

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In anything with the form XはYです, です is a politeness indicator for a sentence with a meaning equivalent to the English sentence, “X is Y”, but です itself does not necessarily mean “is”. It can be a confusing concept to native English speakers but XはY already has the meaning of “X is Y” even without です.

You probably know that だ is also used in some sentences where です would be appropriate, but there is something pretty important you need to know; they don’t have the same meaning.

犬は黒い だ would be incorrect because い adjectives already have the “is” meaning and putting だ on top which also has the meaning sounds weird.

犬は黒いです is correct because です at the end is not adding any additional meaning to the sentence.

Don’t worry about it too much. This concept will come naturally later.

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