Vaisesika Sūtra 1.2.7

सदिति यतो द्रव्यगुणकर्मसु सा सत्ता ॥७॥

saditi yatō dravyaguṇakarmasu sā sattā ॥7॥

[सत् इति यतो द्रव्य गुण कर्मसु सा सत्ता॥
sat iti = thus called "sat", i.e. truth or existence; yatō = if; dravya = substances; guṇa = qualities; karmasu = actions; sā = those; sattā = exists;॥]

It is called "sat", i.e. truth, i.e. existence, if those substances, qualities, and actions exist.