This is the 2601st most frequent Spanish word.
cuantos
"Cuantos" means "how many" in English.
The word 'cuántos' here is used as an interrogative adjective modifying the noun 'libros,' asking for the quantity of books.
¿Cuántos libros tienes en tu colección?
How many books do you have in your collection?
In this sentence, 'cuántos' functions similarly as an interrogative adjective, but it is used declaratively to express understanding of the quantity implied.
Entiendo cuántos problemas has enfrentado.
I understand how many problems you have faced.
Here, 'cuántos' is used in an indirect question structure, inquiring about the number of 'them' attending an event.