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