A tenancy in common (TIC) is one of three types of concurrent estates (defined as an estate that has shared ownership, in which each owner owns a share of the property). The other two types are a joint tenancy and a tenancy by the entirety. A TIC typically has no right of survivorship. This means that if A and B are tenants in common of Blackacre, and A dies, A's share does not to go B. Rather, A's share goes to the party selected in A's will.
In a TIC, the shares in the property may be of unequal size, and can be freely transferred to other owners both during the owner's lifetime and via a will. Even if owners own unequal shares, all owners still have have the right to occupy and use all of the property.
For example, if A and B own a house as tenants in common, and A owns 1/3 of the house and B owns 2/3, they both have the right to occupy the entire property. Further, if B sells his 2/3 share of the home to C, A still retains his 1/3 share in the house.
Property law can be particular with the language required to make certain conveyances of property. To convey property to two parties as tenants in common, property law prefers this language: "O conveys X property to A and B as tenants in common."
Further, if a conveyance does not explicitly show an intent to create a right of survivorship, and it is unclear as to whether the conveyor intended to create a tenancy in common or a joint tenancy, courts will typically interpret the conveyance as creating a tenancy in common, rather than a joint tenancy.