Remember that in Spanish there are 4 different ways to say ‘the’ and ‘a’ where in English we only have 1. This is due to masculine/feminine and singular/plural.
Indefinite Article = ‘a’
a boy= un chico some boys = unos chicos
a girl = una chica some girls = unas chicas
Definite Article = ‘the’
the boy = el chico the boys = los chicos
the girl = la chica the girls = las chicas
Links to practice with: