Kanji for “eternity”

Eternity as a promise, as technical permanence, or as a vast span of time.

永遠 eien

Closest natural translation · misunderstanding risk Low

Reading: eien — Common compound reading
About the reading: The ordinary word for forever.
Literal meaning: Eternity, forever
What it suggests: Time without end, used freely of love, memory and loss.
When to use it: For eternity in the everyday romantic or memorial sense.
On its own: Natural as a complete noun.
In compounds: Natural in 永遠に (forever).
As a tattoo: Common on tattoos and immediately understood. Two balanced kanji.

永久 eikyū

Related meaning, not a literal translation · misunderstanding risk Medium

Reading: eikyū — Common compound reading
About the reading: A standard word, but it dominates technical and legal contexts.
Literal meaning: Permanence, perpetuity
What it suggests: Permanent in a factual sense — permanent teeth, a permanent ban. Less romantic than 永遠.
When to use it: For permanence as a fact rather than a sentiment.
On its own: Natural as a complete noun.
In compounds: Natural in 永久歯 (adult teeth) and 永久追放 (permanent ban).
As a tattoo: Correct but administrative; readers may hear a regulation.
Worth knowing: Used mainly for technical permanence, not for eternal love.

悠久 yūkyū

Symbolic choice, not a literal translation · misunderstanding risk Low

Reading: yūkyū — Common compound reading; literary
About the reading: A literary compound, common in writing about history and nature.
Literal meaning: Vast, unhurried span of time
What it suggests: Time on the scale of mountains and civilisations. Grand and calm rather than personal.
When to use it: For eternity as something vast rather than something promised.
On its own: Natural as a formal noun.
In compounds: Natural in 悠久の歴史 (a long and ancient history).
As a tattoo: Elegant and unusual; it reads as poetry rather than a vow.

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