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