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