महाभारतः mahābhārataḥ - book-1, chapter-70, verse-43

पौरवेणाथ वयसा राजा यौवनमास्थितः ।
यायातेनापि वयसा राज्यं पूरुरकारयत् ॥४३॥

43. pauraveṇātha vayasā rājā yauvanamāsthitaḥ ,
yāyātenāpi vayasā rājyaṁ pūrurakārayat.

43. pauraveṇa atha vayasā rājā yauvanam āsthitaḥ
yāyātena api vayasā rājyam pūruḥ akārayat

43. Then, King (Yayāti), having obtained youth by means of Puru's age, made Puru rule the kingdom, even though Puru now possessed Yayāti's (old) age.

Words meanings summery:

• पौरवेण (pauraveṇa) - by Puru (by Paurava, by Puru)

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

• वयसा (vayasā) - by means of Puru's youthful age (by age, with age, by means of youth)

• राजा (rājā) - King Yayāti (king)

• यौवनम् (yauvanam) - youth (youth, juvenility, prime of life)

• आस्थितः (āsthitaḥ) - having attained (youth) (stood upon, attained, taken up, assumed)

• यायातेन (yāyātena) - by Yayāti (referring to his old age) (by Yayāti)

• अपि (api) - even (even, also, too)

• वयसा (vayasā) - by means of Yayāti's old age (by age, with age)

• राज्यम् (rājyam) - the kingdom, kingship (kingdom, kingship, sovereignty)

• पूरुः (pūruḥ) - Puru (Puru (name))

• अकारयत् (akārayat) - made (Puru) rule (caused to do, caused to be made, caused to rule)

Words meanings and morphology

पौरवेण (pauraveṇa) - by Puru (by Paurava, by Puru)

(noun)

Instrumental, masculine, singular of paurava

paurava - descendant of Puru, relating to Puru; often refers to Puru himself in this context

patronymic derivation from Puru

Note: Refers to Puru, the son of Yayāti.

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

(indeclinable)

वयसा (vayasā) - by means of Puru's youthful age (by age, with age, by means of youth)

(noun)

Instrumental, neuter, singular of vayas

vayas - age, strength, vigor, youth, life, period of life

Note: Refers to the youthful age taken by Yayāti.

राजा (rājā) - King Yayāti (king)

(noun)

Nominative, masculine, singular of rājan

rājan - king, ruler, sovereign

Note: Refers to King Yayāti.

यौवनम् (yauvanam) - youth (youth, juvenility, prime of life)

(noun)

Accusative, neuter, singular of yauvana

yauvana - youth, juvenility, prime of life

from yuvan (young) + aṇa (taddhita suffix)

Note: Object of `āsthitaḥ`.

आस्थितः (āsthitaḥ) - having attained (youth) (stood upon, attained, taken up, assumed)

(adjective)

Nominative, masculine, singular of āsthita

āsthita - placed upon, standing on, resorted to, attained, assumed, fixed, firm

Past Passive Participle

from ā-√sthā (to stand upon, to resort to, to attain)

Prefix: ā

Root: sthā (class 1)

Note: Effectively, 'having attained'.

यायातेन (yāyātena) - by Yayāti (referring to his old age) (by Yayāti)

(proper noun)

Instrumental, masculine, singular of yāyāti

yāyāti - a proper noun, name of a famous king

Note: Refers to King Yayāti's old age that Puru took.

अपि (api) - even (even, also, too)

(indeclinable)

Note: Emphasizes the contrast (Puru took old age).

वयसा (vayasā) - by means of Yayāti's old age (by age, with age)

(noun)

Instrumental, neuter, singular of vayas

vayas - age, strength, vigor, youth, life, period of life

Note: Refers to the old age taken by Puru.

राज्यम् (rājyam) - the kingdom, kingship (kingdom, kingship, sovereignty)

(noun)

Accusative, neuter, singular of rājya

rājya - kingdom, kingship, sovereignty, reign

from rājan (king) + ya (taddhita suffix)

Note: Object of `akārayat`.

पूरुः (pūruḥ) - Puru (Puru (name))

(proper noun)

Nominative, masculine, singular of pūru

pūru - a proper noun, name of a king, son of Yayāti

Note: Subject of `akārayat`.

अकारयत् (akārayat) - made (Puru) rule (caused to do, caused to be made, caused to rule)

(verb)

3rd person , singular, active, past imperfect (laṅ) of kārayat

Causative

Imperfect, 3rd person singular, causative active

Root: kṛ (class 8)

Note: 'Puru caused to rule' implies Puru was made to rule or Puru ruled. Given the context (Yayāti made Puru king), it's 'made Puru rule'.