योगवासिष्ठः yogavāsiṣṭhaḥ - book-7, chapter-2, verse-21

गुल्फवन्ति दृढाङ्गानि सुत्वञ्चि मसृणानि च ।
तेषामपि च मूलानि विद्धि बुद्धीन्द्रियाणि हि ॥ २१ ॥

gulphavanti dṛḍhāṅgāni sutvañci masṛṇāni ca ,
teṣāmapi ca mūlāni viddhi buddhīndriyāṇi hi 21

21. gulphavanti dṛḍhāṅgāni sutvañci masṛṇāni ca
teṣām api ca mūlāni viddhi buddhīndriyāṇi hi

21. hi teṣām api mūlāni buddhīndriyāṇi viddhi ca
gulphavanti dṛḍhāṅgāni sutvañci masṛṇāni ca

21. Know that their roots are indeed the organs of intellect (buddhīndriyāṇi), even those parts which are jointed, have strong constituents, are well-skinned, and smooth.

Words meanings summery:

• गुल्फवन्ति (gulphavanti) - having ankles; having joints; having knots

• दृढाङ्गानि (dṛḍhāṅgāni) - having strong limbs; having strong body; having strong constituents

• सुत्वञ्चि (sutvañci) - well-skinned; having good skin; smooth-skinned

• मसृणानि (masṛṇāni) - smooth, soft, sleek, polished

• च (ca) - and, also

• तेषाम् (teṣām) - of those (roots/organs) (of them, to them)

• अपि (api) - even, also, too

• च (ca) - and, also

• मूलानि (mūlāni) - roots, origins, foundations

• विद्धि (viddhi) - know, understand, perceive

• बुद्धीन्द्रियाणि (buddhīndriyāṇi) - organs of intellect; organs of knowledge; cognitive senses

• हि (hi) - indeed, surely, certainly

Words meanings and morphology

गुल्फवन्ति (gulphavanti) - having ankles; having joints; having knots

(adjective)

Nominative, neuter, plural of gulphavat

gulphavat - having ankles; having joints; having knots

suffix -vat added to gulpha

दृढाङ्गानि (dṛḍhāṅgāni) - having strong limbs; having strong body; having strong constituents

(adjective)

Nominative, neuter, plural of dṛḍhāṅga

dṛḍhāṅga - strong-limbed; strong-bodied; having strong constituents

Compound type : bahuvrīhi (dṛḍha+aṅga)

• dṛḍha – firm, strong, hard, solid
  adjective (masculine)
  Past Passive Participle
  from root dṛh
  Root: dṛh (class 1)
• aṅga – limb, body, part, constituent
  noun (neuter)

सुत्वञ्चि (sutvañci) - well-skinned; having good skin; smooth-skinned

(adjective)

Nominative, neuter, plural of sutvañc

sutvañc - well-skinned; having good skin; smooth-skinned

Compound type : bahuvrīhi (su+tvac)

• su – good, well, excellent
  indeclinable
• tvac – skin, hide
  noun (feminine)

मसृणानि (masṛṇāni) - smooth, soft, sleek, polished

(adjective)

Nominative, neuter, plural of masṛṇa

masṛṇa - smooth, soft, sleek, polished

च (ca) - and, also

(indeclinable)

तेषाम् (teṣām) - of those (roots/organs) (of them, to them)

(pronoun)

Genitive, neuter, plural of tad

tad - that, those

अपि (api) - even, also, too

(indeclinable)

च (ca) - and, also

(indeclinable)

मूलानि (mūlāni) - roots, origins, foundations

(noun)

Accusative, neuter, plural of mūla

mūla - root, origin, foundation, base

Note: object of the verb 'viddhi'

विद्धि (viddhi) - know, understand, perceive

(verb)

2nd person , singular, active, imperative (loṭ) of vid

Root: vid (class 2)

बुद्धीन्द्रियाणि (buddhīndriyāṇi) - organs of intellect; organs of knowledge; cognitive senses

(noun)

Nominative, neuter, plural of buddhīndriya

buddhīndriya - organ of intellect, organ of knowledge, cognitive sense

Compound type : tatpuruṣa (buddhi+indriya)

• buddhi – intellect, understanding, perception, reason
  noun (feminine)
  Root: budh (class 1)
• indriya – sense organ, faculty of sense
  noun (neuter)

Note: predicate nominative, 'know X to be Y'

हि (hi) - indeed, surely, certainly

(indeclinable)