Yoga Sutra 3.02 meditation is continuity of the idea of the meditation

Sūtra III.2

Continuity of the mind there is dhyāna (meditation)

Meditation is continuity of the idea of the meditation-object in that place – a stream of similar ideas untouched by any other idea.

Continuity of the idea in that place is meditation, in that place; for instance the navel circle and the other objects of dhāraṇā. continuity of the idea of the meditation-object, such as the place previously selected for meditation, means a stream of similar ideas, a stream of like ideas as a unity, a continuity of ideas untouched not disturbed by any other idea of opposite kind. That is dhyāna.

Whereas dhāraṇā is touched by other ideas imagined about the object, even though the mind has been settled on that object of meditation alone – if made on the sun, its orbit and extreme brilliance are also the object of the concentration, for the mind is functioning on the location as a pure mental process – not so with dhyāna, for there it is only the stream of a single idea, untouched by any other idea of different kind.