Ad rem is a Latin phrase that is often used in formal writing to indicate relevance or pertinence to the matter at hand. There are several synonyms for ad rem that can be used to convey the same meaning. One such synonym is "relevant," which suggests direct applicability to the subject being discussed. Another possible synonym is "germane," which implies close correlation or connection to the topic. "Pertinent" is another word that can be used in place of ad rem and conveys a sense of directly addressing the issue at hand. Other potential synonyms include "applicable," "appropriate," and "material." All of these words can be used to help clarify the relevance of a particular point or argument in a discussion.