महाभारतः mahābhārataḥ - book-5, chapter-94, verse-42

नरनारायणौ यौ तौ तावेवार्जुनकेशवौ ।
विजानीहि महाराज प्रवीरौ पुरुषर्षभौ ॥४२॥

42. naranārāyaṇau yau tau tāvevārjunakeśavau ,
vijānīhi mahārāja pravīrau puruṣarṣabhau.

42. naranārāyaṇau yau tau tau eva arjunakeśavau
vijānīhi mahārāja pravīrau puruṣarṣabhau

42. O great king, understand that those two, Nara and Nārāyaṇa, are indeed those very two, Arjuna and Keśava (Krishna), the two great heroes and foremost among men (puruṣa).

Words meanings summery:

• नरनारायणौ (naranārāyaṇau) - The divine sages Nara and Nārāyaṇa (who are incarnate as Arjuna and Krishna) (Nara and Nārāyaṇa)

• यौ (yau) - those two who (whichever two, who (dual))

• तौ (tau) - those two

• तौ (tau) - those two

• एव (eva) - indeed, none other than (indeed, only, just)

• अर्जुनकेशवौ (arjunakeśavau) - Arjuna and Keśava (Krishna) (incarnations of Nara and Nārāyaṇa) (Arjuna and Keśava (Krishna))

• विजानीहि (vijānīhi) - know, understand, recognize

• महाराज (mahārāja) - O Dhṛtarāṣṭra! (or general address to a king) (O great king!)

• प्रवीरौ (pravīrau) - two great heroes, two excellent warriors

• पुरुषर्षभौ (puruṣarṣabhau) - two bulls among men, two excellent men, two foremost of men (puruṣa)

Words meanings and morphology

नरनारायणौ (naranārāyaṇau) - The divine sages Nara and Nārāyaṇa (who are incarnate as Arjuna and Krishna) (Nara and Nārāyaṇa)

(proper noun)

Nominative, masculine, dual of naranārāyaṇa

naranārāyaṇa - Nara and Nārāyaṇa (dual deity)

Compound type : Dvandva (nara+nārāyaṇa)

• nara – man, human, primeval man
  noun (masculine)
• nārāyaṇa – Nārāyaṇa (Viṣṇu), son of Nara, moving in waters
  proper noun (masculine)

Note: Predicate nominative with implied 'are'.

यौ (yau) - those two who (whichever two, who (dual))

(pronoun)

Nominative, masculine, dual of yad

yad - which, what, who, that

तौ (tau) - those two

(pronoun)

Nominative, masculine, dual of tad

tad - that, those

तौ (tau) - those two

(pronoun)

Nominative, masculine, dual of tad

tad - that, those

एव (eva) - indeed, none other than (indeed, only, just)

(indeclinable)

अर्जुनकेशवौ (arjunakeśavau) - Arjuna and Keśava (Krishna) (incarnations of Nara and Nārāyaṇa) (Arjuna and Keśava (Krishna))

(proper noun)

Nominative, masculine, dual of arjunakeśava

arjunakeśava - Arjuna and Keśava

Compound type : Dvandva (arjuna+keśava)

• arjuna – Arjuna (a Pāṇḍava prince)
  proper noun (masculine)
• keśava – Keśava (an epithet of Viṣṇu/Kṛṣṇa), having fine hair, slayer of the demon Keśī
  proper noun (masculine)

Note: Predicate nominative with implied 'are'.

विजानीहि (vijānīhi) - know, understand, recognize

(verb)

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

Imperative

Parasmaipada, 2nd person singular (from vi + jñā (9th class) with imperative ending)

Prefix: vi

Root: jñā (class 9)

महाराज (mahārāja) - O Dhṛtarāṣṭra! (or general address to a king) (O great king!)

(noun)

Vocative, masculine, singular of mahārājan

mahārājan - great king, emperor

Vocative singular of mahārājan.

Compound type : Karmadhāraya (mahā+rājan)

• mahā – great, large
  adjective
• rājan – king
  noun (masculine)

प्रवीरौ (pravīrau) - two great heroes, two excellent warriors

(noun)

Nominative, masculine, dual of pravīra

pravīra - great hero, excellent warrior

From pra (excellent) + vīra (hero).

Compound type : Karmadhāraya (pra+vīra)

• pra – forth, forward, excellent
  indeclinable
• vīra – hero, warrior, valiant
  noun (masculine)

Note: Appositive to 'arjunakeśavau'.

पुरुषर्षभौ (puruṣarṣabhau) - two bulls among men, two excellent men, two foremost of men (puruṣa)

(noun)

Nominative, masculine, dual of puruṣarṣabha

puruṣarṣabha - bull among men, chief of men, excellent man (puruṣa)

Compound type : Tatpuruṣa (puruṣa+ṛṣabha)

• puruṣa – man, person, cosmic person (puruṣa)
  noun (masculine)
• ṛṣabha – bull, chief, best, excellent
  noun (masculine)

Note: Appositive to 'arjunakeśavau'.