IPA: /ˌsɛmpɪˈtɜrnəli/
KK: /sɛmpɪˈtɜrnəli/
In a way that lasts forever or for an infinite amount of time.
The love they shared felt sempiternally strong, as if it would never fade away.
Sempiternally → It is formed from "semper" (meaning always) and "aeternus" (meaning eternal). The word "sempiternally" means in a manner that is always eternal or everlasting.
Think of 'always' ('semper') and 'eternal' ('aeternus') to remember that 'sempiternally' refers to something that lasts forever.