DHIAN/ DHYAN
It means steadfast concentration without any break. It is one of the eight steps in Ashtanga Yoga (the eightfold discipline of Yoga), in which one concentrates on some object in order to keep one away from everything else. It means undisturbed flow of thought round the object of meditation.
A Sikh need not practice this type of Yoga and Dhian; and, for a Sikh Guru and God are the only objects of concentration.
(Dr Harjinder Singh Dilgeer)