很可惜当时我们的爱情结束得那么突然，那一直是我心中的一个遗憾。
Let's use a little imagination as I love doing that when explaining Chinese. You know what 可愛 is, right. It's lovable, adorable; 可信 is believable, 可行 is doable. 可惜？惜 is treasuring something. So we can guess that 可惜 is something we want to treasure but it's gone, so we feel it's a pity. 可惜 is a adjective.
遺憾 literally is "leave a regret", so we use it to describe something it leaves a regret in our heart. It can be adjective or noun.
Hope this helps!
Ying Ying
(more)Let's use a little imagination as I love doing that when explaining Chinese. You know what 可愛 is, right. It's lovable, adorable; 可信 is believable, 可行 is doable. 可惜？惜 is treasuring something. So we can guess that 可惜 is something we want to treasure but it's gone, so we feel it's a pity. 可惜 is a adjective.
遺憾 literally is "leave a regret", so we use it to describe something it leaves a regret in our heart. It can be adjective or noun.
Hope this helps!
Ying Ying