Co-joining refers to the act of joining two or more things together. The opposite of co-joining would be separating or disjoining. Other antonyms for co-joining could include detaching, disconnecting, splitting, disassociating, dissociating, uncoupling, and severing. These words imply a disconnection rather than a connection. For instance, when a couple decides to separate, they are disjoining rather than co-joining. Similarly, when an object is split into two or more parts, it is no longer co-joined. Antonyms play a critical role in helping readers understand the opposite meaning of words and are an essential part of expanding one's vocabulary.