This is the 485th most frequent Spanish word.
buenos
"Buenos" means "good" (plural, masculine).
Here, 'buenos' is an adjective describing the noun 'zapatos' (shoes), emphasizing their quality as 'good' shoes.
Estos son unos buenos zapatos.
These are some good shoes.
In this context, 'buenos' modifies 'motivos' (reasons), implying that the reasons are favorable or positive.
Hay buenos motivos para celebrar.
There are good reasons to celebrate.
In this sentence, 'buenos' is part of the greeting 'buenos días,' meaning 'good morning,' which is a standard way to greet in Spanish during the morning hours.