The word "un-substantialities" means lack of substance or importance. Its antonyms are words that refer to something that is significant, meaningful or relevant. Some possible antonyms for this word are solid, substantial, significant, real, important, essential, necessary, valuable, and meaningful. These words are commonly used to describe something that has a tangible or measurable value, or that is essential to achieving a particular goal or objective. For example, a substantial amount of money is needed to run a successful business, and a significant amount of effort is required to achieve a major project goal. Understanding the antonyms of "un-substantialities" can help writers and speakers to convey a clearer message and express their thoughts more effectively.