immortal adj.

word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."

In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.

Proto-Indo-European root meaning "to rub away, harm." Possibly identical with the root *mer- that means "to die" and forms words referring to death and to beings subject to death.

It forms all or part of: amaranth; ambrosia; amortize; Amritsar; immortal; manticore; marasmus; mare (n.3) "night-goblin, incubus;" morbid; mordacious; mordant; moribund; morsel; mort (n.2) "note sounded on a horn at the death of the quarry;" mortal; mortality; mortar; mortgage; mortify; mortmain; mortuary; murder; murrain; nightmare; post-mortem; remorse.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit mrnati "crushes, bruises," mriyate "to kill," martave "to die," mrta- "died, dead," mrtih "death," martah "mortal man," amrta- "immortal;" Avestan miriia- "to die," miryeite "dies," Old Persian martiya- "man;" Hittite mer- "to disappear, vanish," marnu- "to make disappear;" Armenian meranim "to die;" Greek marainein "to consume, exhaust, put out, quench," marasmus "consumption," emorten "died," brotos "mortal" (hence ambrotos "immortal"); Latin mors (genitive mortis) "death," mori "to die;" Armenian merani- "to die;" Gothic maurþr, Old English morþ "murder;" Old Irish marb, Welsh marw "dead;" Lithuanian mirti "to die," mirtis "death;" Old Church Slavonic mreti "to die," mrutvu "dead;" Russian mertvyj, Serbo-Croatian mrtav "dead."