Definition[]
Superfinity (σ) is a fictional infinity created by NO! in the video 0toATE, and then featured in later videos. It is the entry exactly after Bear's Number, but before Megafinity in 0toATE. Superfinity also occurs in SuperWindows78's video 0to[???], after Bear's Number. In 0to[???] however there are some additional numbers between Bear's Number and Superfinity. There are only 3: Fork's Number, Super Number, and NS. In 0to[???] both Bear's Number and Superfinity occur long before Terminus, but a little while after Absolute Everything. This places this number in Class III, as it's greater than AE but less than Terminus.
Lastly Superfinity also appears in the video 0toNever[1/2]. Mathis gives it the symbol σ, the lower case sigma, which makes sense since superfinity starts with s, and sigma is the greek letter s.
Neither NO! nor SuperWindows78 provided any definition for Superfinity so it has to be roughly inferred. NO! names earlier numbers on the pattern of [blank]-finity. It can be assumed that just as infinity is the smallest infinite number, it follows that superfinity is the smallest superfinite number. What does this mean exactly? It's uncertain for a number of reasons. First off because we do not know how many types of numbers comes after finite and infinite numbers according to NO!'s classification system. Furthermore since none of these classes or types of numbers have any definition to begin with, even if we knew how many there were, there would be no way of saying how large each class actually was. This concept is very similar to the idea of "Orders" seen starting in Class 5.
One further clue is that Bear's Number comes immediately after U, UI, UII, U^I, and U^^^I. This suggests some kind of notation for describing fictional infinities of some sort. Bear's Number may be a supremum of this sequence, or it may lie somewhere within the hierarchy. In either case Superfinity likely lies above any such constructions. NS may be a new construction after the UI notation, or it may be a special inaccessible of the UI notation.