योगवासिष्ठः yogavāsiṣṭhaḥ - book-3, chapter-6, verse-21

अध्यात्मविद्या विद्यानां प्रधानं तत्कथाश्रयम् ।
शास्त्रं सच्छास्त्रमित्याहुर्मुच्यते तद्विचारणात् ॥ २१ ॥

adhyātmavidyā vidyānāṃ pradhānaṃ tatkathāśrayam ,
śāstraṃ sacchāstramityāhurmucyate tadvicāraṇāt 21

21. adhyātmavidyā vidyānām pradhānam tatkathāśrayam |
śāstram sacchāstram iti āhuḥ mucyate tat vicāraṇāt ||

21. vidyānām adhyātmavidyā pradhānam,
tatkathāśrayam śāstram sacchāstram iti āhuḥ.
tat vicāraṇāt mucyate.

21. Among all branches of knowledge (vidyā), the knowledge of the supreme self (adhyātma-vidyā) is considered paramount. Any scripture (śāstra) that is founded upon discussions of this knowledge is called a true scripture (sac-chāstra); by reflecting on it, one achieves liberation (mokṣa).

Words meanings summery:

• अध्यात्मविद्या (adhyātmavidyā) - knowledge of the supreme self (adhyātma-vidyā) (spiritual knowledge, knowledge of the self (ātman))

• विद्यानाम् (vidyānām) - among all branches of knowledge (vidyā) (of knowledge disciplines, among sciences)

• प्रधानम् (pradhānam) - paramount (chief, primary, principal)

• तत्कथाश्रयम् (tatkathāśrayam) - founded upon discussions of this knowledge (i.e., adhyātma-vidyā) (based on its discussions/narrations, relying on its topics)

• शास्त्रम् (śāstram) - scripture (śāstra) (scripture, treatise, injunction)

• सच्छास्त्रम् (sacchāstram) - a true scripture (sac-chāstra) (true scripture, good treatise)

• इति (iti) - indicating designation (thus, so, indicating direct speech or quotation)

• आहुः (āhuḥ) - they call (they say, they call)

• मुच्यते (mucyate) - one achieves liberation (one is liberated, it is released)

• तत् (tat) - that (referring to `sacchāstram`) (that, it)

• विचारणात् (vicāraṇāt) - by reflecting on it (from deliberation, from reflection, by inquiry)

Words meanings and morphology

अध्यात्मविद्या (adhyātmavidyā) - knowledge of the supreme self (adhyātma-vidyā) (spiritual knowledge, knowledge of the self (ātman))

(noun)

Nominative, feminine, singular of adhyātmavidyā

adhyātmavidyā - spiritual knowledge, knowledge of the self

Compound type : karmadhāraya (adhyātman+vidyā)

• adhyātman – supreme self, inner self, spirit
  noun (neuter)
• vidyā – knowledge, science, learning
  noun (feminine)
  Root: vid (class 2)

विद्यानाम् (vidyānām) - among all branches of knowledge (vidyā) (of knowledge disciplines, among sciences)

(noun)

Genitive, feminine, plural of vidyā

vidyā - knowledge, science, learning

Root: vid (class 2)

प्रधानम् (pradhānam) - paramount (chief, primary, principal)

(adjective)

Nominative, neuter, singular of pradhāna

pradhāna - chief, principal, primary

Root: dhā (class 3)

तत्कथाश्रयम् (tatkathāśrayam) - founded upon discussions of this knowledge (i.e., adhyātma-vidyā) (based on its discussions/narrations, relying on its topics)

(adjective)

Nominative, neuter, singular of tatkathāśraya

tatkathāśraya - relying on its discussions

Compound type : tatpuruṣa (tad+kathā+āśraya)

• tad – that, its
  pronoun (neuter)
• kathā – story, discussion, narration
  noun (feminine)
  Root: kath (class 10)
• āśraya – reliance, resort, foundation
  noun (masculine)
  From `ā-śri` (to rely on)
  Prefix: ā
  Root: śri (class 1)

Note: It modifies `śāstram`.

शास्त्रम् (śāstram) - scripture (śāstra) (scripture, treatise, injunction)

(noun)

Nominative, neuter, singular of śāstra

śāstra - scripture, treatise, rule

Root: śās (class 2)

सच्छास्त्रम् (sacchāstram) - a true scripture (sac-chāstra) (true scripture, good treatise)

(noun)

Nominative, neuter, singular of sacchāstra

sacchāstra - true scripture, good treatise

Compound type : karmadhāraya (sat+śāstra)

• sat – true, good, existing
  adjective (neuter)
  Present Active Participle
  From root `as` (to be)
  Root: as (class 2)
• śāstra – scripture, treatise, rule
  noun (neuter)
  Root: śās (class 2)

इति (iti) - indicating designation (thus, so, indicating direct speech or quotation)

(indeclinable)

आहुः (āhuḥ) - they call (they say, they call)

(verb)

3rd person , plural, active, perfect (lit) of vac

Irregular perfect tense form (Lit) `āha`, `āhatus`, `āhuḥ`

Root: vac (class 2)

Note: It's an irregular perfect (liṭ) form of `vac` which often functions as a present tense.

मुच्यते (mucyate) - one achieves liberation (one is liberated, it is released)

(verb)

3rd person , singular, passive, present (laṭ) of muc

Root `muc` in passive voice, ātmanepada

Root: muc (class 6)

Note: 3rd person singular, passive voice, present tense.

तत् (tat) - that (referring to `sacchāstram`) (that, it)

(pronoun)

Accusative, neuter, singular of tad

tad - that, it

विचारणात् (vicāraṇāt) - by reflecting on it (from deliberation, from reflection, by inquiry)

(noun)

Ablative, feminine, singular of vicāraṇā

vicāraṇā - deliberation, reflection, inquiry

Feminine noun formed from root `car` (to move, to think) with `vi` and `ā` prefixes, and `ana` suffix

Prefixes: vi+ā

Root: car (class 1)