aeternus

Latin

For older aeviternus, from aevum, from Proto-Indo-European *h₂eyu- (“long time, lifetime”). Morphologically (but not semantically) equivalent to aetās +‎ -rnus.

aeternus (feminine aeterna, neuter aeternum, adverb aeternō); first/second-declension adjective

abiding, lasting, permanent, perpetual
Synonyms: perennis, assiduus, continuātus, perpetuus, diuturnus
- Lucius Annaeus Seneca, Hercules Furens:
  Non prata viridi laeta facie germinant,/nec adulta leni fluctuat Zephyro seges;/non ulla ramos silva pomiferos habet;/sterilis profundi vastitas squalet soli/et foeda tellus torpet aeterno situ— rerumque maestus finis et mundi ultima.
  "No meadows bud, joyous with verdant, / mature waves in the gentle west wind, nor crop; / there is no grove of fruit bearing branches to regard; / barren: and the abysmal fields lie all untilled, / and the foul land lies torpid in abiding sufferance- sad end of things, and the world 's last."
endless, eternal
immortal
Synonym: immortālis

Case / Gender	Masculine	Feminine	Neuter	Masculine	Feminine	Neuter
Number	Singular			Plural
Nominative	aeternus	aeterna	aeternum	aeternī	aeternae	aeterna
Genitive	aeternī	aeternae	aeternī	aeternōrum	aeternārum	aeternōrum
Dative	aeternō	aeternae	aeternō	aeternīs
Accusative	aeternum	aeternam	aeternum	aeternōs	aeternās	aeterna
Ablative	aeternō	aeternā	aeternō	aeternīs
Vocative	aeterne	aeterna	aeternum	aeternī	aeternae	aeterna