Growing up, Jordan Ellenberg didn’t much like geometry. “As a kid I was very interested in math but I was drawn to the more algebraic and numerical side,” said Ellenberg, a professor of mathematics at the University of Wisconsin. Now, he added, “it’s a central part of my life as a scientist” and the subject of his latest book, “Shape: The Hidden Geometry of Information, Biology, Strategy, Democracy, and Everything Else.”

Both in his own research (his specialty is number theory) and in writing about math for a popular audience (in articles and his previous book, “How Not to Be Wrong”), Ellenberg said he kept encountering geometry. “Writing about mathematical aspects of the world and news and people’s lives, I constantly found myself reaching for geometric metaphors, geometric analogies, geometric ideas,” he said.

Some of those ideas seem simple but lead to vexing questions; one example in the book asks readers how many holes are in a straw. “Part of the reason that question is hard to answer is that there’s not really a definition of what counts as a hole,” Ellenberg said. “I think some people think mathematics is about knowing what the exact definition of everything is: what is a hole, what is a circle. No, in mathematics we choose our definitions.”

Part of the story of geometry is the people who asked those questions and came up with definitions. “The reality is that math is made of people,” he said. “Every concept, however abstract, was invented by a person in order to do something.”

What about readers who are a little bit frightened of math? Ellenberg wants them, too. “I really try to write books that can be read at many different speeds and on many different levels and that work on different levels,” he said. And hey, he also learned new things writing the book. “It’s kind of boring to write about what you already know and learning new stuff is much more interesting and exciting and fun.”

*Jordan Ellenberg will read 5 p.m. Wednesday in a virtual event hosted by **Harvard Book Store**.*