Heart appears as the first element in a couple dozen compounds, but the nouns are divided between open compounds (like “heart attack”) and closed compounds (as in the case of heartache), and a couple of adjectives are hyphenated (as with heart-healthy). Is there any method to the madness for these differing styles? Generally, terms associated literally with the central component of the circulatory system are closed compounds, while those with figurative meanings are open.
Compounds having to do with the blood-pumping organ include “heart attack,” “heart disease,” and “heart rate.” Heartbeat is an exception in form, but the term is also used figuratively, as in “I’d go in a heartbeat” to refer to how quickly one would travel somewhere if given the chance. The closed compound heartburn, meanwhile, refers to a condition of the body, but it’s a colloquial term for indigestion that has nothing to do with the heart. (The pain is centered in the esophagus, which is close to the heart.)
Nonliteral usage includes numerous nouns referring to love and its complications, including heartache and heartthrob, as well as adjectives for emotions surrounding positive feelings, such as heartfelt and heartwarming, that are closed. The only one of these words that has multiple part-of-speech variations is heartbreak: Heartbreaker refers to someone who habitually causes heartbreak, and a victim of such a person is heartbroken, though this emotion is also associated with disappointment (“She was heartbroken about not getting the job”) or betrayal (“Smith’s failure to support him left him feeling heartbroken”); the adjectival form is heartbreaking and the adverbial form is heartbreakingly.
Other closed compounds allude to the heart as the core of the body, as in heartland to refer to the central part of a landmass, with a connotation that the region represents industriousness or other traditional values, and heartwood, which denotes the core of a tree. (The heartwood of a pine tree is called heart pine.) A type of fruit is called heart cherry, based on its physical resemblance to the stylized image of a heart, and a similarly shaped shellfish is called a heart cockle.
Besides the adjective heart-healthy, the only hyphenated compound in which heart is the first element is the rarely used adjective heart-free, to refer to someone who is not in love and thus is less likely to become heartbroken.