योगवासिष्ठः yogavāsiṣṭhaḥ - book-7, chapter-139, verse-21

तेन सार्धमहं तत्र तच्चित्तेनैकतां गतः ।
सुषुप्तनिद्रां सुघनां गुणीभूतोऽनुभूतवान् ॥ २१ ॥

tena sārdhamahaṃ tatra taccittenaikatāṃ gataḥ ,
suṣuptanidrāṃ sughanāṃ guṇībhūto'nubhūtavān 21

21. tena sārdham aham tatra tat-cittena ekatām gataḥ
suṣupta-nidrām su-ghanām guṇībhūtaḥ anubhūtavān

21. aham tena sārdham tatra tat-cittena ekatām gataḥ
su-ghanām suṣupta-nidrām guṇībhūtaḥ anubhūtavān

21. Along with him, my mind there became unified with that (supreme consciousness). I experienced a very profound state of deep sleep (suṣupti), having become completely absorbed in it.

Words meanings summery:

• तेन (tena) - with him (the guru or divine principle) (by him, with him, by that)

• सार्धम् (sārdham) - with, together with

• अहम् (aham) - I

• तत्र (tatra) - there, in that place

• तत्-चित्तेन (tat-cittena) - my mind, unified with that (supreme consciousness) (by the mind focused on that, with mind on that)

• एकताम् (ekatām) - oneness, unity

• गतः (gataḥ) - having attained (gone, attained, reached, become)

• सुषुप्त-निद्राम् (suṣupta-nidrām) - a state of deep sleep (suṣupti) (deep sleep, the sleep of suṣupti)

• सु-घनाम् (su-ghanām) - very profound (state) (very dense, profound, very deep)

• गुणीभूतः (guṇībhūtaḥ) - having become completely absorbed in it (as a quality) (having become a quality, having become secondary, absorbed in qualities)

• अनुभूतवान् (anubhūtavān) - experienced

Words meanings and morphology

तेन (tena) - with him (the guru or divine principle) (by him, with him, by that)

(pronoun)

Instrumental, masculine, singular of tad

tad - that, he, she, it

Note: Refers to the 'him' previously mentioned or implied, likely a guru or a divine principle.

सार्धम् (sārdham) - with, together with

(indeclinable)

Note: Often takes instrumental case.

अहम् (aham) - I

(pronoun)

Nominative, singular of aham

aham - I

तत्र (tatra) - there, in that place

(indeclinable)

तत्-चित्तेन (tat-cittena) - my mind, unified with that (supreme consciousness) (by the mind focused on that, with mind on that)

(adjective)

Instrumental, masculine, singular of tat-citta

tat-citta - mind focused on that, having that as mind, absorbed in that

Compound type : bahuvrīhi (tad+citta)

• tad – that
  pronoun (neuter/masculine)
• citta – mind, consciousness, thought
  noun (neuter)
  Root: cit (class 1)

Note: Agreeing with the implied subject 'aham'.

एकताम् (ekatām) - oneness, unity

(noun)

Accusative, feminine, singular of ekatā

ekatā - oneness, unity, identity

गतः (gataḥ) - having attained (gone, attained, reached, become)

(adjective)

Nominative, masculine, singular of gata

gata - gone, obtained, reached, become

Past Passive Participle

Root: gam (class 1)

Note: Functions as a perfect participle, 'having gone/attained'.

सुषुप्त-निद्राम् (suṣupta-nidrām) - a state of deep sleep (suṣupti) (deep sleep, the sleep of suṣupti)

(noun)

Accusative, feminine, singular of suṣupta-nidrā

suṣupta-nidrā - deep sleep, the sleep state called suṣupti

Compound type : tatpuruṣa (suṣupta+nidrā)

• suṣupta – deep sleep, asleep
  adjective (neuter)
  Past Passive Participle
  Prefix: su
  Root: svap (class 2)
• nidrā – sleep, slumber
  noun (feminine)

सु-घनाम् (su-ghanām) - very profound (state) (very dense, profound, very deep)

(adjective)

Accusative, feminine, singular of su-ghana

su-ghana - very dense, very deep, profound

Compound type : karmadhāraya (su+ghana)

• su – good, well, very, excellent
  indeclinable
• ghana – dense, solid, thick, profound
  adjective (masculine/neuter)

Note: Agrees with 'suṣupta-nidrām'.

गुणीभूतः (guṇībhūtaḥ) - having become completely absorbed in it (as a quality) (having become a quality, having become secondary, absorbed in qualities)

(adjective)

Nominative, masculine, singular of guṇībhūta

guṇībhūta - having become a quality, having become secondary, endowed with qualities, absorbed in qualities

Past Passive Participle

Derived from the denominative verb 'guṇībhū' (to become a quality/secondary) with the suffix 'kta'.

Root: bhū (class 1)

Note: Predicative use, agreeing with 'aham'.

अनुभूतवान् (anubhūtavān) - experienced

(adjective)

Nominative, masculine, singular of anubhūtavat

anubhūtavat - one who has experienced

Past Active Participle (ktavatu)

Prefix: anu

Root: bhū (class 1)

Note: Functions as a finite verb in this context, 'I experienced'.