Recent discussions regarding the emerging field of cyber warfare have focused on the term “cyberspace,” and have included cyberspace as being considered its own war fighting domain, much like air, land, sea, and space. In this stage of the Information Age, the international community is grappling with whether it needs to define this information realm as a domain, similar to the air, land, sea, and outer space domains that already exist. History shows that there is always an advantage in a conflict to the side that understands and operates within a domain better than the opponent. In this paper, the authors propose a definition of a domain, define what constitutes a domain, posit how new domains are created over time, and describe the features of what is and is not a domain. These definitions and features lead to our proposal that the “Information Sphere” should the preferred international term, and it is this “InfoSphere” that qualifies as a new domain, with features both similar to and different from the four existing physical domains.