This is the 2627th most frequent Portuguese word.
juro
"Juro" means "interest" (as in financial interest).
The word 'juro' here is used as a verb meaning 'I swear', used to express a strong promise or guarantee.
Eu juro que farei meu melhor.
I swear that I will do my best.
The word 'juro' in this sentence refers to 'interest rate', commonly used in financial contexts.
O banco oferece um juro anual de 5%.
The bank offers an annual interest rate of 5%.
This usage of 'juro' reiterates a promise in short, affirming one's statement emphatically.