▪ I. ir-1
assimilated form in L. of the prefix in-2 before initial r, used in the same way in Eng., as in ir-radiate, ir-ruption. In these derivatives only one r is pronounced.
▪ II. ir-2
assimilated form in L. of the prefix in-3 before initial r, used in the same way in Eng. (and much more frequent than ir-1); as in ir-rational, ir-reclaimable, ir-recoverable, ir-refragable, ir-religion, ir-revocable. In these only one r is pronounced, the prefix being really reduced to i-.