The phrase "appertaining to" means "belonging to" or "related to" something. There are several synonyms that can be used in its place, such as "pertaining to," "related to," "connected to," "associated with," "relevant to," or "corresponding to." These words are interchangeable and can be used in different contexts depending on the situation. For example, "pertaining to" can be used to describe something specific, while "associated with" can be used to describe something more general. Other synonyms for "appertaining to" include "concerning," "regarding," "touching on," and "having to do with." Overall, these synonyms can help to add variety and clarity to one's writing.