BG Chap 18 - Arjuna's question about sannyāsa and tyāga

Arjuna remained unclear when Kṛṣṇa used the word sannyāsa in statements such as sarva-karmāṇi manasā sannyasyāste sukham vaśī – renouncing all actions mentally, the soul resides happily (BG 5.13), and when He used the word tyāga in statements such as tyaktvā karma-phalāsaṅgaṁ – giving up all attachment to the results of actions (BG 4.20). Also Kṛṣṇa had recently stated that those with a desire for liberation, the sannyāsīs, utter the name ‘tat’, and sarva karma-phala-tyāgaṁ - there are others who give up all results (tyāga) of work with great attention (BG 12.11). Arjuna wanted to know if the two words tyāga and sannyāsa have completely different meanings like stones and trees, or do they have similar meanings like Kurus and Pāṇḍavas. Arjuna said that Hṛṣīkeśa, the controller of the senses, had made this doubt arise in him being the instigator of intelligence, and just as the Lord killed Keśi, He could kill this doubt also.