Formal:
* निष्ठा (nishtha): This is the most common and formal way to say loyalty.
* वफ़ादारी (vafaadari): This also means loyalty but carries a connotation of faithfulness and unwavering commitment.
Informal:
* वफ़ादार (vafaadaar): This is the adjective form of "vafaadari" meaning "loyal".
* भक्ति (bhakti): This word implies a strong sense of devotion and dedication, often used in the context of religious loyalty.
* समर्पण (samarpan): This word means "dedication" and implies a complete commitment to something or someone.
The best way to choose the right word depends on the situation. For example, you might say "nishtha" when talking about a company's loyalty to its customers, but "vafaadari" when describing a friend's loyalty.