The phrase "chief part" refers to the most important or prominent aspect of something. Synonyms for this term may vary depending on the context, but some common alternatives include "majority," "primary focus," "dominant feature," "central component," "main ingredient," "essential element," and "core aspect." These synonyms can be used to describe the foundational or primary aspect of something, such as the chief part of a building, the chief part of a speech, or the chief part of a problem. Choosing the appropriate synonym can enhance the clarity and precision of your writing, allowing you to convey your ideas more effectively.