The noun form of the word 'Negotiable' is -

• The noun form of the word 'Negotiable' is - Negotiation.

• Negotiable (adjective)
English Meaning: capable of being traversed, dealt with, or accomplished.
Bangla Meaning: আলাপ-আলোচনার দ্বারা মীমাংসা করা যায় এমন; আপসে মীমাংসনীয়; আলাপ-আলোচনা সাপেক্ষ; আপসে নিষ্পত্তিযোগ্য।

Other forms:
- Negotiation (noun),
- Negotiability (noun),
- Negotiate (verb),
- Negotiator (noun),
- Negotiatory (adjective).

Source: 
1. merriam-webster.
2. Accessible Dictionary by Bangla Academy.