It can also refer to a "partner" in a relationship, particularly in the context of marriage.
Here are some examples of how "sathiya" is used:
* Mera sathiya: My companion/friend
* Tere sathiya: Your companion/friend
* Hum dono sathiya hain: We are both companions/friends
* Mera jeevan sathiya: My life partner
It's a very positive and affectionate term that conveys a close and trusting relationship.