Hello,

I can say with confidence, and chemically talking, that "quinolinone" and "quinolone" refer to the same kind of molecule (a carbonyl group inserted in a position of the quinoline structure).

Other substituents eventually present in the structure should always be specified. I have attached a simple image with some examples.

It is wrong instead to say "quinolone" meaning "x-hydroxy-y-quinolinone/quinolone": such an important substituent should always be specified.

It might happens, on the other hand, that someone who uses frequently a dihydro-derivative does not specify the dihydration in an informal language (I still think it should be better to say at least "dihydroquinolinone" even without specifying the positions).

Regards

P.S. remember that a tautomerisation takes place; see https://en.wikipedia.org/wiki/2-_and_4-Quinolones.

2-Quinolone and 2-quinolinone are the same thing.

Similar compounds have many different names when using different chemical nomenclature. For example: UPAC Name is 1H-quinolin-2-one, MeSH Synonyms is 2-Hydroxyquinoline.

You can find also another names for them: 2-Quinolinol; Carbostyril; Quinolin-2-ol;; Quinolin-2(1H)-one, etc.

I do not see any structural difference between 2-quinolinone and 2-quinolone. The former is also known as 1H-quinolin-2-one and Its  tautomeric form is named as 2-hydroxyquinoline or quinolin-2-ol. Similar is the case with 2-quinolone.

Both are diferent tautomeric form of the same compound.

yes, I agree, the 2-quinolinone and 2-quinolone is same.It is easier to write and represent molecule as 2-quinolone for nomenclature.(a carbonyl group inserted in a position of the quinoline structure).

There is no structural difference between them hence the two name are for the same compound

The structureis the same but, according to the IUPAC nomenclature system, I recommend pyridinone and quinolinone instead of pyridone and quinolone. We say ethanone and not ethone