योगवासिष्ठः yogavāsiṣṭhaḥ - book-6, chapter-81, verse-111

प्राणोऽग्निरुष्णप्रकृतिरपानः शीतलः शशी ।
छायातपवदित्येतौ संस्थितौ मुखमार्गगौ ॥ १११ ॥

prāṇo'gniruṣṇaprakṛtirapānaḥ śītalaḥ śaśī ,
chāyātapavadityetau saṃsthitau mukhamārgagau 111

111. prāṇaḥ agniḥ uṣṇaprakṛtiḥ apānaḥ śītalaḥ śaśī
chāyātapavat iti etau saṃsthitau mukhamārgagau

111. prāṇaḥ agniḥ uṣṇaprakṛtiḥ apānaḥ śītalaḥ śaśī
iti etau chāyātapavat mukhamārgagau saṃsthitau

111. Prāṇa (the vital breath) is Agni, possessing a hot intrinsic nature (prakṛti); Apāna (the downward vital breath) is cool, like the moon. These two are thus situated, moving through the mouth passage, like shade and sun.

Words meanings summery:

• प्राणः (prāṇaḥ) - Refers to one of the five vital airs (prāṇas) in the body, specifically the upward-moving breath. (vital breath, life-force, outgoing breath)

• अग्निः (agniḥ) - The principle of heat and transformation. (fire, Agni (deity))

• उष्णप्रकृतिः (uṣṇaprakṛtiḥ) - of hot nature, having a hot intrinsic nature

• अपानः (apānaḥ) - Refers to one of the five vital airs (prāṇas), specifically the downward-moving breath. (downward breath, vital air)

• शीतलः (śītalaḥ) - cool, cold

• शशी (śaśī) - Here, refers to the moon, symbolizing coolness. (moon, rabbit (moon-bearer))

• छायातपवत् (chāyātapavat) - like shade and sun, like shadow and heat

• इति (iti) - Introduces a simile or consequence. (thus, in this manner, so)

• एतौ (etau) - Refers to Prāṇa and Apāna. (these two)

• संस्थितौ (saṁsthitau) - situated, established, dwelling

• मुखमार्गगौ (mukhamārgagau) - Referring to Prāṇa and Apāna's movement related to respiration. (moving through the mouth passage)

Words meanings and morphology

प्राणः (prāṇaḥ) - Refers to one of the five vital airs (prāṇas) in the body, specifically the upward-moving breath. (vital breath, life-force, outgoing breath)

(noun)

Nominative, masculine, singular of prāṇa

prāṇa - breath, life, vital air, energy, spirit

From root an- (to breathe) with prefix pra-.

Prefix: pra

Root: an (class 2)

अग्निः (agniḥ) - The principle of heat and transformation. (fire, Agni (deity))

(noun)

Nominative, masculine, singular of agni

agni - fire, Agni (Vedic deity), digestive fire

उष्णप्रकृतिः (uṣṇaprakṛtiḥ) - of hot nature, having a hot intrinsic nature

(adjective)

Nominative, masculine, singular of uṣṇaprakṛti

uṣṇaprakṛti - having a hot nature, naturally hot, of hot intrinsic nature

Bahuvrīhi compound: uṣṇā prakṛtiḥ yasya saḥ (one whose nature is hot).

Compound type : bahuvrīhi (uṣṇa+prakṛti)

• uṣṇa – hot, warm, fiery
  adjective
  From root uṣ- (to burn).
  Root: uṣ (class 1)
• prakṛti – nature, intrinsic nature, original form, primordial matter (prakṛti)
  noun (feminine)
  From root kṛ- (to make) with prefix pra-.
  Prefix: pra
  Root: kṛ (class 8)

Note: Agrees with prāṇaḥ.

अपानः (apānaḥ) - Refers to one of the five vital airs (prāṇas), specifically the downward-moving breath. (downward breath, vital air)

(noun)

Nominative, masculine, singular of apāna

apāna - downward breath, vital air that moves downwards, excretion

From root an- (to breathe) with prefix apa-.

Prefix: apa

Root: an (class 2)

शीतलः (śītalaḥ) - cool, cold

(adjective)

Nominative, masculine, singular of śītala

śītala - cool, cold, refreshing, tranquil

From śīta (cold) with suffix -la.

Note: Agrees with apānaḥ.

शशी (śaśī) - Here, refers to the moon, symbolizing coolness. (moon, rabbit (moon-bearer))

(noun)

Nominative, masculine, singular of śaśin

śaśin - moon (lit. 'possessing a rabbit' due to marks on its surface), rabbit

From śaśa (rabbit) with possessive suffix -in.

छायातपवत् (chāyātapavat) - like shade and sun, like shadow and heat

(indeclinable)

Formed by adding the suffix -vat ('like', 'as if') to the dvandva compound 'chāyātapa'.

Compound type : dvandva (chāyā+ātapa)

• chāyā – shade, shadow, reflection, image
  noun (feminine)
• ātapa – sunshine, heat, warmth
  noun (masculine)
  From root tap- (to heat, suffer) with prefix ā-.
  Prefix: ā
  Root: tap (class 1)

इति (iti) - Introduces a simile or consequence. (thus, in this manner, so)

(indeclinable)

Particle.

एतौ (etau) - Refers to Prāṇa and Apāna. (these two)

(pronoun)

Nominative, masculine, dual of etad

etad - this, these (demonstrative pronoun)

Demonstrative pronoun, masculine dual nominative.

संस्थितौ (saṁsthitau) - situated, established, dwelling

(adjective)

Nominative, masculine, dual of saṃsthita

saṁsthita - situated, established, fixed, dwelling, existing

Past Passive Participle

From root sthā- (to stand) with prefix sam-.

Prefix: sam

Root: sthā (class 1)

Note: Agrees with etau (Prāṇa and Apāna).

मुखमार्गगौ (mukhamārgagau) - Referring to Prāṇa and Apāna's movement related to respiration. (moving through the mouth passage)

(adjective)

Nominative, masculine, dual of mukhamārgaga

mukhamārgaga - going through the mouth passage, moving via the oral path

Compound. 'ga' (from root gam- 'to go') is the final member.

Compound type : tatpuruṣa (mukha+mārga+ga)

• mukha – mouth, face, opening
  noun (neuter)
• mārga – path, way, passage, road
  noun (masculine)
  From root mṛj- (to wipe, clean), meaning a cleared path.
  Root: mṛj (class 2)
• ga – going, moving, moving in or through
  adjective
  agent noun/derivative
  From root gam- (to go) + suffix -a.
  Root: gam (class 1)

Note: Agrees with etau.