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