"Sadhana is the practice of Yoga. Tapasya is the concentration of the will to get the results of sadhana and to conquer the lower nature. Aradhana is worship of the Divine, love, self-surrender, aspiration to the Divine, calling the name, prayer. Dhyana is inner concentration of the consciousness, meditation, going inside in Samadhi. Dhyana, Tapasya and Aradhana are all parts of sadhana."
Sri Aurobindo Lights on Yoga, Bases of Sadhana