योगवासिष्ठः yogavāsiṣṭhaḥ - book-6, chapter-33, verse-31

परमात्मतया द्वित्वं न किलात्मनि विद्यते ।
अविकारादिमत्त्वेन सर्वगत्वेन सर्वदा ॥ ३१ ॥

paramātmatayā dvitvaṃ na kilātmani vidyate ,
avikārādimattvena sarvagatvena sarvadā 31

31. paramātmatayā dvitvam na kila ātmani vidyate
avikārādimattvena sarvagatvena sarvadā

31. ātmani dvitvam paramātmatayā kila na vidyate
avikārādimattvena sarvagatvena sarvadā

31. Duality (dvitva) certainly does not exist in the self (ātman) by virtue of its nature as the supreme self (paramātman), for it is always unchanging, beginningless, and all-pervading.

Words meanings summery:

• परमात्मतया (paramātmatayā) - by the nature of the supreme self (paramātman), as the supreme self

• द्वित्वम् (dvitvam) - duality, twoness

• न (na) - not, no

• किल (kila) - indeed, certainly, surely (an emphatic particle)

• आत्मनि (ātmani) - in the self (ātman), in the soul

• विद्यते (vidyate) - exists, is found, is present

• अविकारादिमत्त्वेन (avikārādimattvena) - by virtue of being unchanging, beginningless, etc., due to having no change and no beginning

• सर्वगत्वेन (sarvagatvena) - by virtue of being all-pervading, due to omnipresence

• सर्वदा (sarvadā) - always, at all times

Words meanings and morphology

परमात्मतया (paramātmatayā) - by the nature of the supreme self (paramātman), as the supreme self

(noun)

Instrumental, feminine, singular of paramātmatā

paramātmatā - the state or nature of being the supreme self (paramātman)

Compound type : tatpurusha (paramātman+tā)

• paramātman – the supreme self (paramātman), universal spirit
  noun (masculine)
• tā – suffix forming abstract nouns, "-ness"
  suffix

द्वित्वम् (dvitvam) - duality, twoness

(noun)

Nominative, neuter, singular of dvitva

dvitva - duality, twoness, being two

न (na) - not, no

(indeclinable)

किल (kila) - indeed, certainly, surely (an emphatic particle)

(indeclinable)

आत्मनि (ātmani) - in the self (ātman), in the soul

(noun)

Locative, masculine, singular of ātman

ātman - the self, soul, spirit, essence (ātman)

विद्यते (vidyate) - exists, is found, is present

(verb)

3rd person , singular, middle, present (laṭ) of vid

Root: vid (class 4)

अविकारादिमत्त्वेन (avikārādimattvena) - by virtue of being unchanging, beginningless, etc., due to having no change and no beginning

(noun)

Instrumental, neuter, singular of avikārādimattva

avikārādimattva - the state of being unchanging, beginningless, etc.

Compound type : tatpurusha (avikāra+ādi+mat+tva)

• avikāra – changeless, immutable, without modification
  adjective (neuter)
• ādi – beginning, starting, etcetera, and so on
  indeclinable (masculine)
• mat – having, possessing (suffix)
  suffix
• tva – suffix forming abstract nouns, "-ness"
  suffix

सर्वगत्वेन (sarvagatvena) - by virtue of being all-pervading, due to omnipresence

(noun)

Instrumental, neuter, singular of sarvagattva

sarvagattva - the state of being all-pervading, omnipresence

Compound type : tatpurusha (sarvaga+tva)

• sarvaga – all-pervading, omnipresent
  adjective (neuter)
  Root: gam (class 1)
• tva – suffix forming abstract nouns, "-ness"
  suffix

सर्वदा (sarvadā) - always, at all times

(indeclinable)

formed from sarva (all) + dā (suffix meaning 'at all times')