[1] 完全修飾ドメイン名 (FQDN) は、 TLD を含む、省略されていないドメイン名です。
[2] ( 版) <https://cabforum.org/wp-content/uploads/BRv1.2.3.pdf#page=10>
Fully-Qualified Domain Name: A Domain Name that includes the labels of all superior nodes in the Internet
Domain Name System.
[3] ワイルドカードを含むものをワイルドカードFQDNと言うことがあります。
[4] .
(末尾の点 = 根ドメイン) で終わるドメイン名を FQDN と呼び、
そうでないものは FQDN でないと言う人もいます。
[5] RFC 7622 - Extensible Messaging and Presence Protocol (XMPP): Address Format ( 版) <https://tools.ietf.org/html/rfc7622>
Informational Note: The term "fully qualified domain name" is not
well defined. In [RFC1034], it is also called an absolute domain
name, and the two terms are associated in [RFC1535]. The earliest
use of the term can be found in [RFC1123]. References to those
older specifications ought not to be construed as limiting the
characters of a fully qualified domain name to the ASCII range;
for example, [RFC5890] mentions that a fully qualified domain name
can contain one or more U-labels.
[6] RFC 7719 - DNS Terminology ( ()) <https://tools.ietf.org/html/rfc7719#section-2>
Fully qualified domain name (FQDN): This is often just a clear way
of saying the same thing as "domain name of a node", as outlined
above. However, the term is ambiguous. Strictly speaking, a
fully qualified domain name would include every label, including
the final, zero-length label of the root: such a name would be
written "www.example.net." (note the terminating dot). But
because every name eventually shares the common root, names are
often written relative to the root (such as "www.example.net") and
are still called "fully qualified". This term first appeared in
[RFC819]. In this document, names are often written relative to
the root.
The need for the term "fully qualified domain name" comes from the
existence of partially qualified domain names, which are names
where some of the right-most names are left off and are understood
only by context.