This is the 98th most frequent Croatian word.
bolesti
"Bolesti" means "diseases" or "illnesses" in English.
'Bolesti' here is the genitive singular form and refers to 'of the disease' as the cause.
Zbog naglog širenja bolesti poduzete su hitne mjere zaštite.
Due to the rapid spread of the disease, emergency protective measures were taken.
Here, 'bolesti' is the plural genitive form of 'bolest', referring to diseases.
Razgovarali smo dugo o izazovima kroničnih bolesti.
We talked for a long time about the challenges of chronic diseases.
In this sentence, 'bolesti' is in the genitive singular form, signifying 'of the illness'.