A conveyance from “O to A and B as joint tenants” may create a joint tenancy, though to be certain a prudent lawyer should include “with right of survivorship.” (A court will presume a tenancy in common was intended absent evidence to the contrary, and in some states, the omission of “with right of survivorship” constitutes a fatal lack of evidence that a joint tenancy was intended). The joint tenancy shares many of the same characteristics as a tenancy in common, but the right of survivorship is an important distinguishing feature. Should A die after the above conveyance, B would automatically take A’s interest in the property, irrespective of any Will A may have left and without regard to the rights of A’s heirs. On the other hand, A can “sever” the joint tenancy by conveying her interest during life. If a severance occurs, A and B will thereafter hold the property as tenants in common (however, if there were originally a 3rd joint tenant, C, as between B and C their relation would still be that of joint tenants). Another distinguishing feature of a joint tenancy (w/ROS) is the traditional requirement that joint tenants take title at the same time, via the same interest, and in equal shares (unity of time, title, and interest). Today, however, some courts give more deference to the conveying party’s intent in determining the interest created, without strict deference to the traditional “four unities” (unity of possession is the other one).
A tenancy by the entireties is basically a joint tenancy w/ROS, except that a fifth unity – marriage – is required. Significantly, however, the neither the husband nor the wife has the ability to sever this tenancy by unilateral action – both must consent to any severance, mortgage, etc.