Is a warrant issued to an inmate currently in prison the same as a detainer?

A detainer is a request from another jurisdiction asking that they notify that jurisdiction that the person is about to be released. Detainer's are often the result of a warrant that has been issued for that inmate. If the warrant is relatively minor, then the detainer may not actually be issued. And not all detainers are the result of warrants: there could be Immigration detainers or detainers from probation and parole, asking the prison to let them know when the person will be released because that inmate is supposed to report to probation once he has been released.