At what point in cheese making is curd no longer 'curd' and considered a cheese? Is it a whey content thing? After a certain amount of time? Just curious.
IMHO, as soon as you induce any type of coagulation, it is cheese and not milk. The distinction between curd and cheese is a little tough because it's a sort of continuum of moisture content, calcium bond degradation due to acid, and proteolysis. So right at coagulation, you have a cheese with a lot of moisture, very little acid, and almost no proteolysis. And as you cut, you have less water retained, more acid (usually), and a tad more proteolysis. At the point you brine, you have a lot less water, usually a lot more acid, more calcium breakdown as a result of acid development, and slightly more proteolysis. More to it, but that's the general idea.
You can similarly consider an aged cheese as just one hunk of curd mass, far along the continuum.