Can I register a 2LD for .com or .net?

For some top-level domains such as .com, .net and .org, second-level domains (2LDs) can be registered. When registering one of these, you define the portion left of the dot.

If you consider a top level domain name, would be a second-level domain name however is usually considered a third-level domain name (3LD) while is the 2LD and .au is the top-level domain name.