Almost no word in the Buddhist tradition has as wide a scope and range of meanings as the Sanskrit word dharma, which is spelled dhamma in Pali. It means different things in different contexts, when used in the singular or the plural, and as an abstract or common noun. The matter is further complicated by the fact that it is also a central term in the Hindu tradition, with a different set of meanings, and it is easy to confound the two.
Most often dharma or dhamma refers to the teachings of the Buddha. In the Southern Buddhist Theravada tradition, these teachings are considered to have been spoken by the historical Buddha in the fifth century BCE and carefully preserved in the Pali language, first orally and then transcribed into texts. The word dhamma in this context refers to this body of literature and the teachings conveyed by it.
In the Northern Buddhist traditions of Tibet and East Asia the concept of dharma has a much wider range, insofar as a vast number of teachers, both human and nonhuman, are considered at any time to be pronouncing a universal message using a broad array of skillful means. The historical Shakyamuni was only one of many teachers conveying the dharma, which in these traditions is increasingly seen as a timeless truth proclaimed through the cosmos of the past, present, and future by many buddhas, bodhisattvas, and other great beings. The universe itself can be viewed as resounding with dharma, as the teachings are embodied even by the singing of birds and the clashing of thunder.
Related: The Many Meanings of Dharma
When used in the plural, the word becomes the term designating mental objects in the Buddhist analysis of experience. Just as sights are what are seen by the eye and sounds are heard with the ear, so too dharmas are the mental objects known by the mind. As philosophical trends moved further away from materialism in the direction of idealism, all phenomena came to be understood as mental phenomena. Thus seen, the entire universe consists of dharmas, impermanent events arising and passing away interdependently, inherently empty of substance and devoid of self. The term can be used in an abstract form, dharmata (dharma-ness or dharma-hood), to express this seminal insight into the very nature of the way things actually are.
In the modern Western world, dharma can simply stand in for “Buddhism” or “Buddhist.” Dharma centers, dharma teachers, dharma practices may vary greatly in substance and appearance, but are all considered to be related in some important way to the Buddhist tradition. And of course, inevitably, just like its siblings Karma, Samsara, and Nirvana, Dharma is a perfume you can easily purchase on the Internet.