Vaisesika Sūtra 10.2.01

कारणमिति द्रव्ये कार्यसमवायात् ॥१॥

kāraṇam iti dravye kārya-samavāyāt ॥1॥

[कारणम् (kāraṇam) - cause; इति (iti) - thus; द्रव्ये (dravye) - in substance; कार्यसमवायात् (kārya-samavāyāt) - due to inherence of the effect;]

In a substance, the cause is so called due to the inherence of the effect.