Sāṃkhya Kārikā verse 3

mūlaprakṛtiḥ avikṛtiḥ mahadādyāḥ prakṛti-vikṛtayaḥ sapta |
ṣoḍaśakaḥ tu vikāraḥ na prakṛtiḥ na vikṛtiḥ puruṣaḥ ||

prakṛti - process of matterpuruṣa - animating principle, self, consciousness, spirit

Commentaries and Reflections

Paul Harvey:

Primordial Nature is uncreated and yet creates.
Awareness is neither.

What I would call a simplified representation, yet one which tries to respect the Saṃskṛta.
Also Sāṃkhya is more focused on exploring the individual in relation to cosmology, hence the use of the terms such as Prakṛti and Puruṣa.
Whilst in contrast to the Yoga Sūtra focuses more on exploring the individual in relation to psychology, hence the use of terms such as Citta and Cit.
Both approaches share a common expression of the interwoven duality of Matter and Spirit.
Thats why they are often associated when looking at the Ṣat Darśana as three pairs.
Mūla (root) Prakṛti is the term used in this particular Śloka to describe Primordial Nature.