What's the plural form of synesthesia? Here's the word you're looking for.
Answer
The noun synesthesia can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be synesthesia.
However, in more specific contexts, the plural form can also be synesthesias e.g. in reference to various types of synesthesias
or a collection of synesthesias.
Examples
Her first book, about synesthesia, titled Tasting the Universe, will be out in March 2011 from New Page Books.
In its own particular way, synesthesia points to yet another way that the wiring of the brain can create different ways to experience life.
In later research, the group established that synesthesia is not only consistent across time but also concretely measurable in the brain.
Some studies have suggested, however, that there may be a complex genetic linkage between synesthesia, autism, and savantism.
Then synesthesia, or experiencing of one sensory modality as another, takes over and the basic somaesthetic image is elaborated into a full OBE with visual imagery.
Is a form of synesthesia at work? Ali Smith, author I don't know about synesthesia.