na-adjective
Describes something that continues indefinitely without a natural end, often used for abstract states, effects, or conditions.
この政策は永続的な効果をもたらすだろう。
This policy will bring about a lasting effect.
平和
Peace is maintained through perpetual effort.
恒久的 also means 'permanent' but is more formal and often used in legal or technical contexts, whereas 永続的 is slightly more common in everyday descriptions.
Compound of 永続 (eizoku, 'continuance') + 的 (-teki, '-like, -ic'), forming an adjectival noun. The exact historical derivation is straightforward.