Definition of Dharma (quote from mahabharat text)

dhāraṇād dharma ityāhuḥ dharmo dhārayate prajāḥ |
ya syād dhāraṇa samyuktaḥ sa dharma iti niścayaḥ ||

Meaning: The word Dharma is derived from dhāraṇa or sustenance; dharma sustains society. That Which has the capacity to sustain is indeed dharma. (Mahabharata, Karna Parva 69:58)
It is the science of conduct, the systematized principles according to which one should act. This is relative to the individual and one’s surroundings and circumstances.

                                                                                                     –Roshan Suvarna