संन्यासस्य महाबाहो तत्त्वमिच्छामि वेदितुम्।त्यागस्य च हृषीकेश पृथक्केशिनिषूदन॥
sannyāsasya mahā-bāho tattvam icchāmi veditumtyāgasya ca hṛṣīkeśa pṛthak keśi-niṣūdana
Word by word
The verse says
Krishna, I want to understand giving up. What renunciation really is, and what letting go of the fruit really is, and how the two differ.
In plain words
Arjuna asks one last question, and it is a good one.
Two words have been used through this whole book and he has noticed they are not the same. Sannyāsa is walking away from the work. Tyāga is doing the work and letting go of what it pays.
He wants the difference stated plainly. After seventeen chapters, that is a reasonable thing to want.
Where you've felt this · in study
Your niece has sat through a whole term of lectures and understood most of it. In the last class she puts her hand up and asks what the difference is between two words the teacher has been using interchangeably since week one. Half the room looks up. Nobody had been willing to admit they were not sure either. She was not behind. She was the only one still checking.
Going deeper
Asking for a definition at the end rather than the beginning is the mark of someone who has actually been listening.
The two words are close enough to blur. Sannyāsa is the older, more dramatic one: putting work down and walking away from household life. Tyāga is quieter and means letting go, specifically of the claim on what the work produces.
Arjuna is not asking out of curiosity. He has a concrete problem. He is being told to fight, and he wants to know whether there is a version of giving up that would let him out of it honourably.
What makes the question honest is that he asks it in the open. Most of us do the opposite with a word we are unsure of. We keep using it, hoping the meaning will become clear from context, and sometimes a whole decision turns on a distinction we never checked.