Answer: The type of word relationship that this analogy shows is synonym.
Explanation: A synonym is a word that is very similar in meaning to another word. However, synonyms differ in spelling and pronounciation; therefore, synonyms are different from homophones. In the analogy provided, the two pairs of words are synonyms. "Cave" and "cavern" have very similar meanings as both refer to a large chamber. Moreover, "song" and "tune" can also be used as synonyms as both of them refer to a piece of music.
