योगवासिष्ठः yogavāsiṣṭhaḥ - book-3, chapter-81, verse-3

यत्संकोचविकासाभ्यां जगत्प्रलयसृष्टयः ।
निष्ठा वेदान्तवाक्यानामथ वाचामगोचरः ॥ ३ ॥

yatsaṃkocavikāsābhyāṃ jagatpralayasṛṣṭayaḥ ,
niṣṭhā vedāntavākyānāmatha vācāmagocaraḥ 3

3. yat saṃkocavikāsābhyām jagat pralayasṛṣṭayaḥ
niṣṭhā vedāntavākyānām atha vācām agocaraḥ

3. yat saṃkocavikāsābhyām jagat pralayasṛṣṭayaḥ
atha vācām agocaraḥ vedāntavākyānām niṣṭhā

3. That reality by whose contraction and expansion the dissolution and creation of the cosmos (jagat) occur, is the ultimate purport of Vedānta statements and is beyond the reach of speech.

Words meanings summery:

• यत् (yat) - that (reality, Brahman) (which, that)

• संकोचविकासाभ्याम् (saṁkocavikāsābhyām) - by contraction and expansion, by folding and unfolding

• जगत् (jagat) - cosmos (jagat) (world, universe, cosmos)

• प्रलयसृष्टयः (pralayasṛṣṭayaḥ) - dissolutions and creations

• निष्ठा (niṣṭhā) - ultimate purport or goal (end, conclusion, ultimate aim, firm conviction)

• वेदान्तवाक्यानाम् (vedāntavākyānām) - of the Vedānta statements, of the Upanishadic texts

• अथ (atha) - and (and, moreover, now, then)

• वाचाम् (vācām) - of words, of speech, of voices

• अगोचरः (agocaraḥ) - beyond the reach or grasp of speech (invisible, imperceptible, inaccessible, beyond the reach)

Words meanings and morphology

यत् (yat) - that (reality, Brahman) (which, that)

(pronoun)

Nominative, neuter, singular of yad

yad - which, what, that

Note: Could also be accusative singular neuter, but nominative fits the context better as the subject of the implied verb 'is'.

संकोचविकासाभ्याम् (saṁkocavikāsābhyām) - by contraction and expansion, by folding and unfolding

(noun)

Instrumental, masculine, dual of saṃkocavikāsa

saṁkocavikāsa - contraction and expansion

Compound type : dvandva (saṃkoca+vikāsa)

• saṃkoca – contraction, shrinking
  noun (masculine)
  Derived from sam-kuc (to contract)
  Prefix: sam
  Root: kuc (class 1)
• vikāsa – expansion, blossoming, development
  noun (masculine)
  Derived from vi-kas (to open, expand)
  Prefix: vi
  Root: kas (class 1)

जगत् (jagat) - cosmos (jagat) (world, universe, cosmos)

(noun)

Nominative, neuter, singular of jagat

jagat - moving, living; world, universe

Present Active Participle

From root gam (to go) + śatṛ suffix, then used as a noun.

Root: gam (class 1)

Note: Here, the world (jagat) is the object of creation and dissolution, but in the sentence structure, it's part of the compound 'jagatpralayasṛṣṭayaḥ' effectively as a qualifier.

प्रलयसृष्टयः (pralayasṛṣṭayaḥ) - dissolutions and creations

(noun)

Nominative, feminine, plural of pralayasṛṣṭi

pralayasṛṣṭi - dissolution and creation

Compound type : dvandva (pralaya+sṛṣṭi)

• pralaya – dissolution, destruction, absorption
  noun (masculine)
  Derived from pra-lī (to dissolve)
  Prefix: pra
  Root: lī (class 4)
• sṛṣṭi – creation, emission
  noun (feminine)
  Derived from root sṛj (to create, emit)
  Root: sṛj (class 6)

Note: It refers to the acts of dissolution and creation of the world (jagat).

निष्ठा (niṣṭhā) - ultimate purport or goal (end, conclusion, ultimate aim, firm conviction)

(noun)

Nominative, feminine, singular of niṣṭhā

niṣṭhā - end, conclusion, firm standing, ultimate aim

Derived from ni-sthā (to stand firm)

Prefix: ni

Root: sthā (class 1)

वेदान्तवाक्यानाम् (vedāntavākyānām) - of the Vedānta statements, of the Upanishadic texts

(noun)

Genitive, neuter, plural of vedāntavākya

vedāntavākya - Vedānta statement

Compound type : tatpuruṣa (vedānta+vākya)

• vedānta – end of the Vedas, Upanishads, Vedānta philosophy
  noun (masculine)
  Compound of veda + anta
• vākya – statement, sentence, speech
  noun (neuter)
  Derived from vac (to speak)
  Root: vac (class 2)

अथ (atha) - and (and, moreover, now, then)

(indeclinable)

Note: Connects the two clauses about its nature.

वाचाम् (vācām) - of words, of speech, of voices

(noun)

Genitive, feminine, plural of vāc

vāc - speech, word, voice

From root vac (to speak)

Root: vac (class 2)

अगोचरः (agocaraḥ) - beyond the reach or grasp of speech (invisible, imperceptible, inaccessible, beyond the reach)

(adjective)

Nominative, masculine, singular of agocara

agocara - invisible, imperceptible, inaccessible to the senses or words

Compound of a (negation) + gocara (perceptible, within reach).

Compound type : nañ-tatpuruṣa (a+gocara)

• a – not, un-
  indeclinable
  Negation prefix.
• gocara – range, sphere, object of sense, perceptible
  noun (masculine)
  Compound of go (sense organ, cow) + cara (moving, going)
  Root: car (class 1)

Note: It refers to the ultimate reality described.