The feature that most distinguishes a joint tenancy from a tenancy in common is:

Both joint tenants and tenants in common hold undivided interests in the property, meaning each owner has an equal right to use the entire property, regardless of their individual share. This characteristic is common to both forms of ownership and does not serve to differentiate them.

Unity of possession refers to the principle that all co-owners have equal rights to possess and use the entire property, which is a shared feature in both joint tenancy and tenancy in common. Therefore, this concept does not set apart the two forms of property ownership.

The right of transfer allows tenants in common to sell or transfer their interest in the property independently. In contrast, joint tenants can only transfer their interest with the consent of the other joint tenants, which can sever the joint tenancy. Consequently, this feature does not serve to differentiate joint tenancy fundamentally from tenancy in common.