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