Order type two

Two is the second ordinal number, with two elements. It is the order type of, among other things, pairs of two numbers where the first number is smaller than the second.

Ordering
Two can be written as the set $$2 = \{ 0, 1 \}$$, which gives the order relation $$\emptyset \in 1 \in 2$$.

Successor Ordinal
Two is the successor ordinal to order type one.