Immortal means never dying. The immortal gods, an immortal soul, nobody is immortal.
It is used literally in myth and religion and figuratively of fame: an immortal line, immortalised in a song. As a noun, an immortal is a god or a figure whose reputation will not fade. Immortality is the state. Note that immortal does not mean invulnerable — many mythologies have immortals who can be killed but not aged; and that immortalise means to make famous permanently, not to make deathless.
1adjectiveimmortalNever dying.
“The gods in that story are immortal and thoroughly bored.”
2adjectivecertainCertain to be remembered for ever.
“The poet's most famous lines have become immortal.”
immortal is a state of not dying.
Latin immortalis is in-, not, plus mortalis, mortal, from mors, death. The Greek equivalent athanatos is built the same way, and Greek myth called the gods simply the deathless ones.
Proto-Indo-European
*mer-
peo
*anauša- — immortal, without death
Ancient Greek
ἀθάνατος
Latin
immortālis
English, today
immortal
Built from
From Latin immortālis, from prefix im- (“not”) (from in-) + mortālis (“mortal”) (from mors (“death”), combining form mort- + adjectival suffix -alis), equivalent to im- + mortal. Displaced native undeadly, from Old English undēadlīċ. The term referring to the Persian soldiers was a Ancient Greek ἀθάνατος. One suggestion claimed that "Immortals" were named by the ancient Greeks because wounded soldiers were quickly replaced, while another claimed that it was because Greek informants confused peo anauša- (“immortal, without death”) with peo anūšiya- (“companion, royal bodyguard”).
Etymology from Wiktionary, CC BY-SA