The term second-level domain name refers to a domain that is in the DNS hierarchy directly below a top-level domain name.
- .uk - this is a top-level domain name, also known as TLD.
- example.uk - this is a second-level domain name.
- example.co.uk - this is a third-level domain name.
In the UK there are 9.4 million third-level domains registered compared to just 2.4 million second-level domains. [Correct as of February 2020]
