(Sanskrit धारणा) Literally, "concentration." In Patajali's Yoga Sutras, dharana is the sixth of the eight steps of yoga, and is the precursor of meditation (dhyana).
"Dharana (concentration) is fixing the consciousness in one place." —Yoga Sutras 3:1
"Concentration or Dharana is centering the mind on one single thought... During concentration, the various rays of the mind are collected and focused on the object of concentration. There will be no tossing of the mind. One idea occupies the mind. The whole energy of the mind is concentrated on that one idea. The senses become still. They do not function. When there is deep concentration, there is no consciousness of the body and surroundings. When you study a book with profound interest, you do not hear if a man shouts and calls you by your name. You do not see a person when he stands in front of you. You do not smell the sweet fragrance of flowers that are placed on the table by your side. This is concentration or one-pointedness of mind. The mind is fixed firmly on one thing. You must have such a deep concentration when you think of God or the Atman." —Swami Sivananda