grammar - is suki an adjective and a verb?

I thought that "suki" was a verb which meant "to like". It is hard to me to make sense why it seems to be always used with "desu".

Now in a webpage I read that suki is an adjective, which means something like "liked" like some sort of passive voice I guess? That's why it uses the verb desu almost always I supposed. But I also see in another webpage that suki is a verb with all its conjugations.

The question is, is it suki an adjective, a verb, or both, and if it's also a verb, when it's used like a verb with its respective conjugations and without desu? (Assuming it can be used without desu.)

Answer

好き suki is a difficult word.

What is clear is that it derives from the verb 好く suku, which is still in use (most often in the passive voice: 好かれる "to be liked").

However, like the 連用形 ren'yōkei "masu-stem" of so many other verbs, it took on a life of its own, primarily as what is quite naturally analyzed as 形容動詞 keiyōdōshi "na-adjective".

Hence we have

1. 
   

   〇〇が好きです
   〇〇 ga suki desu
   
   _{cf. 〇〇がきれいです}

   
   


2. 
   

   好きな〇〇
   suki na 〇〇
   _{cf. きれいな〇〇}

   
   

A literal translation might be "X is likeable/nice", which equates to "I like X".

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Note that 嫌い kirai (from 嫌う kirau, also often seen in the passive 嫌われる) works almost exactly the same.