First, the expression of emotions is very bad. "No trace" is an adjective to describe how deep the heartache is. In a word, it hurts, it hurts! Reach the extreme.
Secondly, there is another meaning that the heartache is not revealed, and there is no trace at all, so that you can't perceive the taste of heartache, and you can't feel it, which means that heartache has reached the extreme.
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Broken Hearts Without Traces is a song in the music album Stealing Hearts released by Jacky Cheung 1994. Judging from the lyrics, the song "Broken Heart Without Trace" needs emotion to sing, and it is not easy for ordinary people to sing well.