ものの - although, notwithstanding

「～だが、しかし」
Although, notwithstanding - although something (to which ものの is attached) is certainly true, the result is not as expected. Seems to appear at the end of quite long phrases or sentences on the two times I have seen it - and liable to confuse if not spotted...

（１）頭ではわかっているものの、実際に使い方を言葉で説明するのは難しい。
Even though I understand it in my head, it is difficult to actually explain the actual way of using it in words.

（２）新しい服を買ったものの、なかなか着ていく機会がない。
Although I bought some new clothes an opportunity to wear then still hasnt come.

（３）祖父は体は丈夫なものの、最近耳が聞こえにくくなってきた。
Although Grandad's body is strong, recently he has had trouble hearing.

普通形　（ナAな・なAである、Nな・Nである）＋ものの