When it comes to describing the most substantial or significant portion of something, there are plenty of synonyms that can be used for the term "major part." A few common alternatives to this phrase include "main component," "core element," "primary ingredient," "dominant feature," and "central aspect." Other variations might include "key factor," "essence," "vital segment," or "fundamental aspect." Depending on the context and what is being described, some other possibilities could include "crucial constituent," "pivotal piece," "defining attribute," "primary focus," or "biggest piece of the pie." Ultimately, there are many different ways to convey the idea of a "major part" when communicating about an object, event, or situation.