The noun motilin can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be motilin.
However, in more specific contexts, the plural form can also be motilins e.g. in reference to various types of motilins or a collection of motilins.
Win Amazon gift cards by writing simple stories at Fictish, a new story writing game backed by WordHippo.
