सद्भावे साधुभावे च सदित्येतत्प्रयुज्यते। प्रशस्ते कर्मणि तथा सच्छब्दः पार्थ युज्यते ॥

sad-bhāve sādhu-bhāve cha sad ity etat prayujyate praśhaste karmaṇi tathā sach-chhabdaḥ pārtha yujyate

" Sat " is used in the sense of reality and goodness; likewise, O Pârtha, the word " Sat " is used in the sense of a good work.

In plain words: Krishna explains that the word "Sat" means what is real and what is good. It is also used to name a good deed. He calls Arjuna "Partha," meaning son of Pritha.