Domain or Domains

[Naruto]

Which keyword is better? domain or domains?

a) domain (for example: mydomain.com, domaindirect.com, domainpeople.com)
b) domains (for example: buydomains.com, greatdomains.com, cheapdomains.com)

 

[cursal]

If you do an overture search for a plural word (domains) it will return the value for the singular (domain)

Form there, you have to decide....

 

[seeker]

overture does not show plurals.
it will almost always show the singular form.

Other than that, it depends on the wording.
in your example, (except for mydomain), all word+domain make more sense with the plural:
buydomains, greatdomains, superbdomains...etc....etc....
when it is reversed (i.e. domainsareus, somainpeople, domainwhatever), the the singular is a must.