Yoga Sūtra Chapter Three verse 2

तत्र प्रत्ययैकतानता ध्यानम् ॥२॥

tatra pratyaya-ekatānatā dhyānam ||2||

There, the continuity of psychic activity is meditation.

tatra - therepratyaya - psychic activity; cause; conception, assumption, notion, idea;ekatānatā - continuitydhyāna - meditation; mental representation of the personal attributes of a deity

Commentaries and Reflections

Commentary by T Krishnamacharya:

Dhyānam is the seventh Aṅga of the Aṣṭāṅga Yoga.
In order to experience Dhyānam, the sixth step,
Dhāraṇā, should have been practiced thoroughly.”

“The state of Dhyānam is possible in a seated posture.
If a person lies down, it may induce sleep.
If a person walks and moves about,
he may be distracted by the objects around him.
This posture must be in a place
where the mind will not be distracted.”

Dhyānam is an activity of a mind
dominated by Sattva linked to Ātma.
So Ātma and Sattva required for Dhyānam to occur.”

“A person who is physically fit and
who has been cleansed by the Agni of Dhyānam
has no fear of sickness, disease, age or death.”

“Just as Mūla BandhaUḍḍīyāna Bandha,
Jālandhara Bandha and Jivha Bandha
are very important for Prāṇāyāma,
Mano Bandha is very important for Dhyānam.
Mano Bandha is Dhyānam.”

Commentary by TKV Desikachar:

“Prāṇāyāma leads to this.
Pratyāhāra, to see without the senses distracting or pulling the mind, and
Dhāraṇā, to see without the mind losing itself, because of colouring or expectations.
Dhyānam arises out of this.”

“Perhaps the best explanation of Dhyāna is given by Patañjali in the Yoga Sūtra Chapter Three verses One and Two, where he states that one must first fix the question (Dhāraṇā) and then link to it (Dhyāna).
One who is not able to fix the question is not able to succeed in Dhyāna.”

Commentary by Paul Harvey:

Dhāraṇā is the process of ‘holding onto’ the object.
Dhyānā is the process of ‘linking with’ the object.
Samādhi is the process of ‘integration into’ the object.”
Reflections on Yoga Sūtra Chapter 3 verses 1-3