योगवासिष्ठः yogavāsiṣṭhaḥ - book-6, chapter-25, verse-4

अपानोऽप्यनिशं ब्रह्मन्स्पन्दशक्तिः सदागतिः ।
सबाह्याभ्यन्तरे देहे त्वपानोऽयमवाक्स्थितः ॥ ४ ॥

apāno'pyaniśaṃ brahmanspandaśaktiḥ sadāgatiḥ ,
sabāhyābhyantare dehe tvapāno'yamavāksthitaḥ 4

4. apānaḥ api aniśam brahman spandaśaktiḥ sadāgatiḥ
sabāhyābhyantare dehe tu apānaḥ ayam avāksthitaḥ

4. brahman api apānaḥ aniśam spandaśaktiḥ sadāgatiḥ.
tu ayam apānaḥ sabāhyābhyantare dehe avāksthitaḥ.

4. O brahmin, the apana (life-breath), which constantly possesses the power of pulsation and is ever-moving, is situated downwards in this body, both externally and internally.

Words meanings summery:

• अपानः (apānaḥ) - apana (life-breath)

• अपि (api) - also, even

• अनिशम् (aniśam) - constantly, unceasingly

• ब्रह्मन् (brahman) - O brahmin

• स्पन्दशक्तिः (spandaśaktiḥ) - power of pulsation

• सदागतिः (sadāgatiḥ) - ever-moving

• सबाह्याभ्यन्तरे (sabāhyābhyantare) - both external and internal

• देहे (dehe) - in the body

• तु (tu) - indeed, but

• अपानः (apānaḥ) - apana (life-breath)

• अयम् (ayam) - this

• अवाक्स्थितः (avāksthitaḥ) - situated downwards

Words meanings and morphology

अपानः (apānaḥ) - apana (life-breath)

(noun)

Nominative, masculine, singular of apāna

apāna - downward-moving breath, one of the five vital airs (prāṇa)

Prefix: apa

Root: an (class 2)

अपि (api) - also, even

(indeclinable)

अनिशम् (aniśam) - constantly, unceasingly

(indeclinable)

Compound type : avyayībhāva (na+niśā)

• na – not, un-
  indeclinable
• niśā – night
  noun (feminine)

Note: Adverbial usage.

ब्रह्मन् (brahman) - O brahmin

(noun)

Vocative, masculine, singular of brahman

brahman - a brahmin, priest, the Absolute (brahman), prayer

Root: bṛh (class 1)

स्पन्दशक्तिः (spandaśaktiḥ) - power of pulsation

(noun)

Nominative, feminine, singular of spandaśakti

spandaśakti - power of vibration, pulsating energy

Compound type : tatpuruṣa (spanda+śakti)

• spanda – vibration, pulsation, motion
  noun (masculine)
  Root: spand (class 1)
• śakti – power, energy, capability (śakti)
  noun (feminine)
  Root: śak (class 5)

सदागतिः (sadāgatiḥ) - ever-moving

(adjective)

Nominative, masculine, singular of sadāgati

sadāgati - always moving, perpetual motion; also wind

Compound type : bahuvrīhi (sadā+gati)

• sadā – always, ever
  indeclinable
• gati – motion, movement, course
  noun (feminine)
  Root: gam (class 1)

सबाह्याभ्यन्तरे (sabāhyābhyantare) - both external and internal

(adjective)

Locative, masculine, singular of sabāhyābhyantara

sabāhyābhyantara - along with the external and internal, outer and inner

Compound type : bahuvrīhi (sa+bāhya+abhyantara)

• sa – with, together with
  indeclinable
• bāhya – external, outer
  adjective (masculine)
• abhyantara – internal, inner
  adjective (masculine)
  Prefixes: abhi+antara

Note: Agrees with 'dehe'.

देहे (dehe) - in the body

(noun)

Locative, masculine, singular of deha

deha - body

Root: dih (class 4)

तु (tu) - indeed, but

(indeclinable)

अपानः (apānaḥ) - apana (life-breath)

(noun)

Nominative, masculine, singular of apāna

apāna - downward-moving breath, one of the five vital airs (prāṇa)

Prefix: apa

Root: an (class 2)

अयम् (ayam) - this

(pronoun)

Nominative, masculine, singular of idam

idam - this, this one

अवाक्स्थितः (avāksthitaḥ) - situated downwards

(adjective)

Nominative, masculine, singular of avāksthita

avāksthita - situated downwards, placed below

Past Passive Participle

From `avas` + `sthita` (root `sthā`). `avas` becomes `avāk` before `s`.

Compound type : tatpuruṣa (avas+sthita)

• avas – down, downwards
  indeclinable
• sthita – stood, situated, existing
  adjective (masculine)
  Past Passive Participle
  Derived from root 'sthā'.
  Root: sthā (class 1)

Note: Participle acting as an adjective.