Reassociation

Lenara Kahn and Jadzia Dax consider reassociation.

Reassociation is the resumption of a romantic relationship between two joined Trill by their subsequent hosts. Since the point of each successive host is for the symbiont to acquire new lifetimes of experiences, Trill consider re-connecting with relationships from a past life "unnatural". Joined Trill who reassociate are exiled from Trill society, and their symbionts die with the current host since they no longer have access to new hosts. This is a dire consequence, since for Trill nothing is more important than protecting the life of the symbiont. (DS9: "Rejoined")

It should be noted that, in the Star Trek: The Next Generation episode The Host, the Odan symbiont appeared willing to rejoin with Beverly Crusher after its transference into a new host, despite the rules of Reassociation. It is speculated that this is because of the relatively short and recent nature of the relationship – either that, or the rule of Reassociation was not yet fully developed at this time. Other possibilities include that Crusher, not being Trill, was exempt from the prohibition, or that the Reassociation law did not apply to Odan's species of Trill, assuming they were a sub-species as suggested by conjectural explanations for differences in appearances and behaviors.