永久 (yǒng jiǔ): everlasting; perpetual; lasting; forever; permanent

Scientists hope that the newly built underwater laboratory can remain permanently on the seabed, providing a long-term base for future deep-sea research.

This historic stone bridge has weathered centuries of storms and still stands firmly across the river, becoming a permanent symbol of the small town.

In order to protect this primeval forest, the government decided to designate the surrounding area as a permanent protected zone, prohibiting all commercial logging activities.

Grandpa placed that family photo in the most prominent spot on his desk; to him, it is a permanently treasured memory that he will never lose no matter where he moves.

After many rounds of negotiations, the two countries finally agreed to designate this disputed area as a permanent demilitarized zone, allowing border residents to live in peace from then on.