Self
The science of superimmortality defines the self as a set of structures and functioning of matter that has the property of producing the same or identical ixperiencitness. But there is also the concept of the partial self where different structures and functionings of matter will produce parts of ixperiencitness that are identical. Two or more parts of an ixperiencitness can be identical with another ixperiencitness where the whole ixperiencitnesses are not identical.
There are also many other definitions of the self that are used in conversations and philosophy. Many people believe that the self is destroyed at death. If the self is defined as the a grouping of structures and functioning of matter that produce a specific ixperiencitness then it is not necessarily permanently destroyed at death. It still can potentially be created in the future or has been created before in the past. Many religious people believe that the self is defined by a singular supernatural soul that is separate from the body and can exist independent of the body. Some believe that the body is inactivated at death but that their god can restore the body at a later date.