sempiternal
Concise Oxford English Dictionary © 2008 Oxford University Press:
sempiternal /ˌsɛmpɪˈtəːn(ə)l/
▶adjective literary eternal and unchanging; everlasting.
– derivatives
sempiternally adverb,
sempiternity noun.
sempiternally adverb,
sempiternity noun.
– origin ME: from OFr. sempiternel or late L. sempiternalis, from L. sempiternus, from semper ‘always’ + aeternus ‘eternal’.
'sempiternal' also found in these Oxford entries:

