Definitions for "Second-level domain"
A domain with a name containing one "dot": for example, "", "" or "". This can be distinguished from a third-level domain, containing two dots (such as ""), a fourth-level domain, containing three dots (such as ""), etc.(ES:Dominio de segundo nivel, IT:Dominio di secondo livello, FR:Domaine de second niveau)
The domain name system is designed as a hierarchy. The root is the highest level of the hierarchy, followed by the top level domain, then followed by the second-level domain. For example, for the domain "", "espn" is the second-level domain, "com" is the top level domain, and the "." is the root.
a child of a first-level domain, and so on