Yoga Sutras of Patanjali 1.10

अभावप्रत्ययालम्बना वृत्तिर्निद्रा ॥

abhava-pratyaya-alambana vrittir nidra

Sleep is that modification of the mind which has the absence of cognition as its support.

अभाव (ज्ञान के अभाव) के प्रत्यय पर आधारित वृत्ति निद्रा है।