不変|ふへんfuhen[0]heiban (flat)

1. na-adjective, no-adjectiveeternal; everlasting; unchangeable; immutable; immovable; constant; permanent; indestructible
   これ不変ふへんの真理しんりなり。↗

   This is an immutable truth.
2. noun, mathinvariant

• Synonym変わらないかわらないNeutralThe plain negative of 変わる; colloquially the usual way to say something doesn't change, past or future, as in 「これからも変わらない」. 「不変」 is more written.
• SynonymコンスタントNeutralLoanword for steady and unvarying; stresses consistent performance, as in 「コンスタントに勝つ」.
• Synonym千古不易せんこふえきWrittenA four-character idiom for what never changes through the ages; solemn written style, used of eternal truths and values.
• SynonymパーマネントNeutralLoanword meaning permanent, but today it mostly means a perm hairstyle, as 「パーマ」; rarely used as an adjective.
• Synonym恒久的こうきゅうてきWrittenWritten word for something permanent and lasting; stresses being kept up over the long term, as in 「恒久平和」.
• Synonym恒常的こうじょうてきWrittenWritten word for something constant and always present; also covers chronic conditions, as in 「恒常的な赤字」.
• Related永続的えいぞくてきWrittenWritten word for something lasting; stresses that it keeps continuing on, as in 「永続的な関係」.
• Antonym変化へんかNeutralChange or alteration; the everyday antonym standing opposite the constancy of 「不変」.
• Antonym変動へんどうWrittenWritten word for fluctuation or movement in a situation; opposite of 「不変」, as in 「価格変動」.
• Antonym可変かへんWrittenWritten, technical term for something variable or adjustable; the direct opposite of 「不変」, as in 「可変抵抗」.

Use 「不変」 for what is essentially constant and never changes, as in 「不変の真理」「不変の愛」. In speech say 「変わらない」. For long-term duration pick 「恒久的」 or 「永続的」, and for steady performance 「コンスタント」. The opposites are 「変化」, 「変動」 and 「可変」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 変かわらないこと。
2. 変かわらない様よう。