From Zenwiki

is cognate of norm (dharma) and form (dharma), which means law/truth and form/phenomena. Dharma thus means 1) form (any phenomena), 2) norm (law found in them), and 3) teaching (mainly the teaching of the Buddha) of it (norm of forms or law of phenomena). The fundamental/central teaching of the Buddha is the Dharma of all dharmas, that is, the Law of Dependent Co-origination, i.e., all phenomena are interdependently originated on causes and conditions (ex. seed and water, air, light, gravity, temperature, etc.).