How to Say "Permanent" in Japanese

恒久的な

kōkyūteki na

恒久的な (kōkyūteki na) is the Japanese word for permanent.

恒久的な describes something that lasts for an indefinitely long time.

Meaning: lasting for an indefinitely long time (adj)

What does it mean word for word?

The root of the word is 恒久 (kōkyū), which literally means 'permanence' or 'eternity'.

恒久的な is the antonym of 一時的な (ichijiteki na), which means temporary.

恒久的な is a na-adjective used to modify nouns.

kōkyūteki na

The concept of permanence in 恒久的な is philosophically opposed to the pervasive Japanese concept of 無常 (mujō). This Buddhist principle teaches that the only constant is impermanence, making the idea of something being truly 恒久的 a radical notion in Japanese thought.
In emotional contexts, such as promising 'eternal love', 恒久的な is replaced by 永久 (eikyū). Using the former in a romantic setting would sound like a legal contract or a government treaty.
While 恒久的な (kōkyūteki na) describes a permanent state, you should never use it to describe a permanent marker or a permanent habit. For those everyday items, Japanese uses entirely different words like 油性 (yūsei) for oil-based pens.

恒久的な平和など幻想に過ぎない。
Permanent peace is nothing but an illusion.
This sentence shows how to describe permanent peace as an illusion using 恒久的な.
Tatoeba #173603 by KK_kaku_, translation #26422 by CK
私たちみんな恒久的な世界平和を願っています。
We all wish for permanent world peace.
This sentence uses 恒久的な to express a wish for world peace.
Tatoeba #164994 by xtofu80, translation #247773 by CK
銀行員の給与カットは一時的なもので、恒久的なものではなかった。
The banker's pay cut was temporary, not permanent.
This sentence contrasts a temporary pay cut with something that is not 恒久的な.
Tatoeba #893254 by thyc244, translation #681716 by Source_VOA
この美しい花は永遠に続く。
This beautiful flower will last forever.
彼の優しさは永遠だ。
His kindness is permanent.
君との思い出はこの胸に永遠に残る。
Memories with you will permanently remain in my heart.

Hiyori and Hiroto are discussing a city planning project.

陽葵 Himari

これは恒久的な施設になる予定ですか？
Kore wa kōkyūtekina shisetsu ni naru yotei desu ka?
Is this planned to be a permanent facility?
大翔 Hiroto

はい、ずっとここに置いておくつもりです。
Hai, zutto koko ni oite oku tsumori desu.
Yes, we intend to keep it here indefinitely.
陽葵 Himari

恒久的な解決策が見つかってよかったですね。
Kōkyūtekina kaiketsusaku ga mitsukatte yokatta desu ne.
It's good that a permanent solution was found.
大翔 Hiroto

本当にそう思います。安心しました。
Hontō ni sō omoimasu. Anshin shimashita.
I really think so too. I'm relieved.

Sources

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