The word "unnecessariness" refers to the state of being unnecessary or not required. Some antonyms for this word are "essentiality," indicating that something is vital or crucial, or "necessity," meaning that something is required or needed. Other antonyms to this word include "relevance," "significance," "importance," or "usefulness," which all convey different connotations of something being important, relevant, or beneficial. Antonyms for "unnecessariness" represent a wide range of meanings, all of which emphasize the opposite of something being unnecessary or superfluous, instead being essential, beneficial, or significant in some way.