What's the plural form of naphthoquinone? Here's the word you're looking for.
Answer
The noun naphthoquinone can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be naphthoquinone.
However, in more specific contexts, the plural form can also be naphthoquinones e.g. in reference to various types of naphthoquinones
or a collection of naphthoquinones.