This is the 3711th most frequent Spanish word.
pertenecen
"Belong (to)."
In this sentence, 'pertenecen' is used to indicate possession or ownership of the books by the library.
Los libros pertenecen a la biblioteca.
The books belong to the library.
Here, 'pertenecen' is applied to express the natural association or native habitat of pandas.
Los pandas pertenecen a las regiones montañosas de China.
Pandas belong to the mountainous regions of China.
In this context, 'pertenecen' is used metaphorically to indicate an association or connection to a certain time period.