He is credited with coining the symbol ∞ for the concept of infinity

One of the interesting facts about John Wallis is that he is credited with coining the symbol ∞ for the concept of infinity. Wallis published a treatise on conic sections in 1655, which defined them analytically. This was the first book to consider and define these curves as curves of the second degree. It helped to dispel some of the misconceptions about René Descartes' work on analytic geometry. Wallis popularized the symbol ∞ of infinity in his Treatise on Conic Sections. "I suppose any plane (following the Geometry of Indivisibles of Cavalieri) to be made up of an infinite number of parallel lines, or as I would prefer, of an infinite number of parallelograms of the same altitude; (let the altitude of each one of these be an infinitely small part 1/∞ of the whole altitude, and let the symbol ∞ denote Infinity) and the altitude of all to make up the altitude of the figure", he wrote.

Infinity is defined as anything that is limitless, endless, or greater than any natural number. It is frequently represented by the infinity symbol ∞. Many philosophers have debated the philosophical nature of infinity since the time of the ancient Greeks. With the introduction of the infinity symbol and the infinitesimal calculus in the 17th century, mathematicians began to work with infinite series and what some mathematicians considered infinitely small quantities, but infinity remained associated with endless processes. As mathematicians struggled with the calculus foundation, it remained unclear whether infinity could be considered a number or magnitude, and if so, how. Georg Cantor expanded the mathematical study of infinity at the end of the nineteenth century by studying infinite sets and infinite numbers, demonstrating that they can be of various sizes. Infinity is a mathematical concept, and infinite mathematical objects, like any other mathematical object, can be studied, manipulated, and used.