JOINT, in law, as applied to obligations, estates, implies that the rights in question relate to the aggregate of the parties joined. Obligations to which several are parties may be several, i.e., enforceable against each independently of the others, or joint, i.e., enforceable only against all of them taken together, or joint and several, i.e., enforceable against each or all at the option of the claimant.. So an interest or estate given to two or more persons for their joint lives continues only so long as all the lives are in existence. Joint-tenants are co-owners who take together at the same time, by the same title, and without any difference in the quality or extent of their respective interests ; and when one of the joint-tenants dies his share, instead of going to his own heirs, lapses to his co-tenants by survivorship. . This estate is therefore to be carefully distinguished from tenancy in common, when the co-tenants have each a separate interest which on death passes to the heirs and not to the surviving tenants. When several take an estate together any words or facts implying severance will prevent the tenancy from being construed as joint.