"Trios" are thoughts expressed by three related words. They may be phrases, sentences, conversations, miniature poems ("triodes"), three pieces of a single word, etc. The three words may be related in any number of ways - homophones, anagrams, word ladders, other logological relations, rhyme, alliteration, repetition. Here's a special type, in the irreverant style of gross grocer grossest. You'll quickly see what I'm up to. It's artificial, sure, but it created the scaffolding for some trios I thought you might enjoy.
"Comparative Homophonic Trios,"
Word Ways: Vol. 41
, Article 16.
Available at: http://digitalcommons.butler.edu/wordways/vol41/iss3/16