expression, noun
unfortunate thing; pity; shame
Used to express regret or disappointment about a situation. Often appears in phrases like 残念なことに (unfortunately) or as a standalone exclamation.
残念なことに、彼は来られなかった。
Unfortunately, he couldn't come.
それは本当に残念なことだ。
That's really a pity.
残念 is a na-adjective meaning 'regrettable' or 'disappointing'. 残念なこと nominalizes it, turning the feeling into a concrete 'unfortunate thing' or 'pity'.
Phrase composed of 残念 (regrettable) + な (attributive form of na-adjective) + こと (thing). The word 残念 itself is a Sino-Japanese compound from 残 (remain) and 念 (thought/feeling), implying lingering regret.