(Sanskrit धर्म; Tibetan chö) A word with many levels of application. Ultimately, "that which upholds." Dharma literally means "law or justice personified, righteousness, duty, merit, statue, practice, religion, observance, relating to justice or virtue, law, thing, ceremony, good works, character, propriety of conduct, morality or ethics, virtue." Thus, the word is used in a wide variety of ways.
Generally: dharma is the inner constitution of a thing, which governs its growth.
The Tibetan version chö implies "change" or "bringing transformation." The spiritual teachings themselves are the Dharma. Likewise, the fruit of good actions, which we receive as compensation, is Dharma. Any great truth is Dharma. In common usage, the word Dharma refers to the teachings of the path to the end of suffering, and to the result of that path. One of the Three Jewels (Tri-ratna).
"स्वाध्यायान् मा प्रमदः।: Satyam Vada (speak the truth), Dharmam Chara (do your duty)." - Taittiriyopanishad
Dharma is the equivilent of the Greek dikaiosynē:
“…take no thought, saying, What shall we eat? or, What shall we drink? or, Wherewithal shall we be clothed? (For after all these things do the ethnos [multitudes] seek:) for your heavenly Father knoweth that ye have need of all these things. But seek ye first the kingdom of Theos, and his dikaiosynē [dharma]; and all these things shall be added unto you.” —Matthew 6