Does "Busen" denote the area between the breasts or the breasts?

As the question in a paradox reading implies (area between (the breasts or the breasts)) the answer is yes--which wouldn't happen with singular "the breast".

Whether the ridge gave a meronym, a subsense, of the more general whole, or vice-versa, is anyhow not part of the question, but still interesting to ask. I'm affraid I cannot decide it, and the thread so far is not completely clear either. The majority seems to think the word had always described tits.

Indeed, -en in most cases shows plural. der Busen would thus be a pluraletantum like die Eltern, and this point is driven further by the lack of a separate plural morpheme in die Busen (which would thus imply two peoples'bosoms). This is just a hint, not compelling evidence, as the English and German forms differ too much, which is expected for ever so slight taboo words. Further consideratiins would have little to do with modern German, so I will skip analogous comparisons of tit and zit.

The question can be parsed as an inclusive or. In that sense, the chest bone area as the center of gravity of the bosom is the anatomical human chest more truly than the "milk bags" that bosom today generally refers to.

Does "Busen" denote the area between the breasts or the breasts?

As the question in a paradox reading implies (area between (the breasts or the breasts)) the answer is yes--which wouldn't happen with singular "the breast".

Whether the ridge gave a meronym, a subsense, of the more general whole, or vice-versa, is anyhow not part of the question, but still interesting to ask. I'm afraid I cannot decide it, and the thread so far is not completely clear either. The majority seems to think the word had always described tits.

Indeed, -en in most cases shows plural. der Busen would thus be a pluraletantum like die Eltern, and this point is driven further by the lack of a separate plural morpheme in die Busen (which would thus imply two peoples'bosoms). This is just a hint, not compelling evidence, as the English and German forms differ too much, which is expected for ever so slight taboo words. Further considerations would have little to do with modern German, so I will skip analogous comparisons of tit and zit.

The question can be parsed as an inclusive or. In that sense, the chest bone area as the center of gravity of the bosom is the anatomical human chest more truly than the "milk bags" that bosom today generally refers to.