In short is a phrase often used to summarize or briefly explain a concept. However, there are several synonyms for this phrase that can be used to add variety and enhance writing. For instance, "to sum up" is a common phrase that means the same thing as "in short". "In a nutshell" is another synonym that can be used to concisely convey a message. "To put it briefly" is another option, implying brevity. The phrase "in brief" can also be used instead of "in short". Overall, these synonyms can be used interchangeably and help to avoid redundancy in writing.