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