Heartburn is a body feeling, not a feeling of the heart. Acid from your stomach comes up and makes an unpleasant burning in your chest or the top of your stomach. It often follows a big meal, spicy food, coffee, or lying down too soon. The name is a trap for learners: it sits near where people think the heart is, so older English called it a burn of the heart, but it is the food pipe and stomach, not the heart muscle. Though actually, because the burn is in the chest, people sometimes worry it is a heart attack — which is why it is worth knowing that the everyday word is about acid, while strange or severe chest pain is a question for a doctor, not for a dictionary. It is a common informal noun. In clinics you may also hear reflux, or GERD for the longer problem that brings heartburn again and again. You get heartburn, have heartburn; it is not sadness, and it is not heartache.