出典:Wiktionary
The etymological antonym of prior is ulterior (from Latin), and the corresponding antonym to prior to is ulterior to (compare primate/ultimate for “first/last”). This is now no longer used, however, and there is no corresponding antonym to express “after”. Typically either subsequent (to) or posterior (to) are used, but these form different pairs – precedent/subsequent and anterior/posterior – and are more formal than prior. For this reason some suggest against using prior to, particularly when it is paired with an antonym, instead using the Germanic before/after.[1][2]