Mancipatio and in iure cessio are methods to acquire the ownership, or, more generally speaking, to acquire the power (not only over the property, but over the persons, as well). Both are defined as formal and abstract proceedings known to the Roman civil law.
However, these legal proceedings resemble each other not only in the above-mentioned characteristics. On the other hand, they differ in many aspects, as well, the most visibly in the form of their performance.
We may divide the position of the mancipatio and in iure cessio in the Roman legal order and the relationship between them into three categories: a) mancipatio and in iure cessio frequently alternate each other (e.g. transfer of the ownership of the res mancipi, Gai Inst. 2, 22); b) both of them shall be used jointly to receive the desired result (adoptio stricto sensu which combines several mancipations with the final in iure cessio - vindicatio from the side of the adopting father, Gai Inst. 1, 134); and c) only one of them shall be used for the relevant purpose and the second one does not suit (e.g. in iure cessio hereditatis, Gai Inst. 3, 85; mancipatio familiae, Gai Inst. 2, 103). The paper addresses the most interesting cases of the resemblance and differences between the mancipatio and in iure cessio briefly explained above in the Institutions of Gaius.