I have a domain DomainA.com and X.DomainA.com is it consider a single domain or multiple domain?
Multiple registration of Domains is when you create multiple Domain names for your website such as '.com' and '.co.uk'. By Daniel
Yes.
GoDaddy.com offers the best and cheapest domain registration. If you purchase a domain for multiple years it will cost about $7.50
Use Universal distribution groups in a multiple-domain environment. The membership of universal distribution groups is replicated to each global catalog server in each domain
A hub has a single collision domain, which is why it can cause problems when network traffic is high.
Tree
A domain is a portion of the overall DNS namespace. A zone, however, can contain multiple contiguous domains.
A domain is bigger than a phyla. A domain is the highest level of biological classification, encompassing multiple kingdoms. Phyla belong within the kingdom level of classification.
A network that consists of multiple domains within the network environment are referred to as a "Forest". An example of this would be a domain named x.com & a domain named y.com that are joined together in a trust relationship to form a multiple domain network, or a "Forest".
Since multiple companies, in multiple states, can use the same name, having the name in the domain name does not give you first rights. If you want to claim the name, you have to be the first to do so.
Canadian Domain offers Canadians a CIRA Certified Domain Registrar. The service allows Canadians to register the websites for .ca. It's around $39 to apply for a domain name and discounts are available for multiple years.