Heartache is a strong, lasting sadness, often mixed with worry. It does not flash and go; it sits in you. People reach for it when something that matters has gone wrong — a love that ended, a family that is breaking, a hope that did not happen. It is heavier than upset and slower than a short cry. You will hear it in songs, in stories, and in everyday talk about love, though it can sound a little older and more literary than plain sadness. It is usually uncountable: so much heartache, a lot of heartache. Writers sometimes use the plural for separate pains, but learners are safer with the uncountable. Though actually, the word still carries a little of the body. Emotional distress can come with tightness or heaviness in the chest, so the ache is not only a picture. That mix of feeling and body is old in the word, and it is why heartache and heartburn look like cousins but are not the same thing at all.