Question : Is samadhi the same as turiya, the fourth state?
Ramana Maharshi : Samadhi, turiya and nirvikalpa all have the same implication, that is, awareness of the Self. Turiya literally means the fourth state, the supreme consciousness, as distinct from the other three states: waking, dreaming and dreamless sleep. The fourth state is eternal and the other three states come and go in it.
In turiya there is the awareness that the mind has merged in its source, the Heart, and is quiescent there, although some thoughts still impinge on it and the senses are still somewhat active. In nirvikalpa the senses are inactive and thoughts are totally absent. Hence the experience of pure consciousness in this state is intense and blissful. Turiya is obtainable in savikalpa samadhi.