The
word dhyana is derived from the root dhi, meaning "intellect".
Meditation involves the channeling of intellect, or mind, to one point.
Dhyana is a continuous succession of identical thoughts directed
toward one object which happens so quickly that before one subsides
another (same thought) takes its place.
Dhyana
is distinguished from dharana (concentration) only by its uninterrupted
nature. In scriptures the difference between concentration and meditation
is described as the difference between pouring water and pouring oil:
both streams fall toward one place, but water falls in a "broken"
stream of drops whereas the stream of oil is smooth, constant, unbroken.