The word "most primogenial" refers to something that is the most original, ancient or first in existence. The antonyms for this word include modern, contemporary and recent, which describe things that are new, current or present-day. Other antonyms include derivative, imitative, and copied, which describe things that are derived or borrowed from other sources, rather than being original. Additionally, terms like secondary, subsequent and later denote something that comes after the first or main thing, while terms like last, ultimate, or final describe the end or last stage of something. Therefore, "most primogenial" and its antonyms are useful in distinguishing between the original and new, as well as marking the beginning and the end of a series.