The prefix "hept-" is used to indicate the number seven. However, there are some other words that can be used as synonyms of "hept-." The word "sept," which also comes from the Latin word septem meaning seven, can be used as an alternative. Another synonym is "septi-" as seen in the word "septilateral," which describes a shape with seven sides. Additionally, "hepta-" and "septuple" are both synonyms for "hept-," with the latter referring to something that is seven times the normal amount. Overall, these synonyms can be used interchangeably with "hept-" depending on the context and intended meaning of the word.