"Work upon" is a commonly used phrase to indicate that someone is putting effort into something or trying to influence it. However, there are several synonyms for this phrase that can be used interchangeably depending on the context. One such synonym is "manipulate," which suggests a more deliberate attempt to control or direct something. Another useful synonym is "impact," which implies that someone or something is having a significant effect on a situation or outcome. Other synonyms include "influence," "shape," and "mold," each of which carries its own connotations and nuances. By using these synonyms in place of "work upon," writers and speakers can add variation and precision to their language.