There are several different groups which speak the Romani language(s). As the Romani spread throughout Europe, they began to diverge into different groups, with

There are several different groups which speak the Romani language(s). As the Romani spread throughout Europe, they began to diverge into different groups, with separate identities, dialects, traditions, etc. These groups have various names, including Rom, Sinti, Kale, Vlax, among others. The term Rom/Roma is ambiguous, because some authors use it to refer to the Romani-speaking groups collectively, others use the term to refer to particular subgroup(s) known by that name, as opposed to other subgroups such as the Sinti. So the above commenter had learned the “synonym for Romani collectively” definition, but is now exposed to the “specific Romani subgroup” definition, and is being introduced to that by people who view the first definition as incorrect. (I’m not much of a linguistic prescriptivist, so not sure if I agree it is “incorrect” per se, but certainly if one dislikes unintended controversy it is better avoided.)