Search for Homophones

That sounds like it would be a SIRIUS undertaking, without maybe just looping in an outside integration to an external system which specializes in such a thing.  Do you have a particular use case in mind?

Ha, ha, 
good example. We are looking for such kind of a search in database fields. For search in documents Solr is already offering capabilities. 
It shouldn't be so bad - according to sources, there are ~ 1200 Homophones in the English language. According to Wikipedia
there are concerning groups of homophones (excluding proper nouns), there are approximately 88 triplets, 24 quadruplets, 2 quintuplets, 1 sextet, 1 septet, and 1 questionable octet (possibly a second septet). 

Meaning if a user types in one of the search phrase which met one of the items in the octet:
raise, rays, rase, raze, rehs, res, reais, [race]
Appian will automatically search for all other ones - but maybe only if the user has check marked the box 'Include Homophones'

Ha, ha, 
good example. We are looking for such kind of a search in database fields. For search in documents Solr is already offering capabilities. 
It shouldn't be so bad - according to sources, there are ~ 1200 Homophones in the English language. According to Wikipedia
there are concerning groups of homophones (excluding proper nouns), there are approximately 88 triplets, 24 quadruplets, 2 quintuplets, 1 sextet, 1 septet, and 1 questionable octet (possibly a second septet). 

Meaning if a user types in one of the search phrase which met one of the items in the octet:
raise, rays, rase, raze, rehs, res, reais, [race]
Appian will automatically search for all other ones - but maybe only if the user has check marked the box 'Include Homophones'