Hacker News Reader

Comment by akerl_ | Hacker News Reader

They can happen at multiple levels of the hierarchy

That just means it is not limited to "top-level" domains. example.foo.com is a domain as foo.com, com.

This feels like you've accidentally waxed pedantic a bit. In common parlance, com is a TLD, example.com is a domain, foo.example.com is a subdomain. The suffix list is designed to capture all of that and maps to how it's used (you take the suffix list and check if anything in it is a suffix map for the name you've been given).

I always thought:

  - com, example.com, foo.example.com are all domains
  - com is a TLD
  - subdomain is a relative term, not an absolute one:
    . example.com is a subdomain of com
    . foo.example.com is a subdomain of example.com
    . bar.foo.example.com is a subdomain of foo.example.com

Yup, you’re correct. But in common usage, it would be weird to refer to example.com as a subdomain. Depending on the context, it would also be weird to refer to foo.example.com as a domain instead of a subdomain.

If somebody asked me what domain you’re using and you said “com”, you would technically have answered accurately but they’d be confused.

OK, makes sense.

Reply on news.ycombinator.com