eternal

adjectives

continuing forever or indefinitely

"the ageless themes of love and revenge"; "eternal truths"; "life everlasting"; "hell's perpetual fires"; "the unending bliss of heaven"

aeonian, ageless, eonian, eternal, everlasting, perpetual, unceasing, unending

is derived from

tiresomely long; seemingly without end

"endless debates"; "an endless conversation"; "the wait seemed eternal"; "eternal quarreling"; "an interminable sermon"

endless, eternal, interminable

is derived from