noun, na-adjective, noun which may take the genitive case particle 'no'
eternal and unchanging; permanence
A yojijukugo emphasizing absolute, timeless constancy. Often used in formal or literary contexts to describe principles, truths, or abstract qualities that never change.
Nothing in this world is eternal and unchanging.
He vowed eternal and unchanging love.
永遠 means 'eternity' and focuses on endless time, while 永久不変 adds the nuance of being completely unchanging.
不変 means 'unchanging' or 'constant', but 永久不変 intensifies this by adding 'eternal'.
A yojijukugo composed of 永久 (eternal) and 不変 (unchanging). The exact historical derivation is uncertain, but it follows a common pattern of combining two two-character compounds to create an emphatic four-character idiom.