This is the 235th most frequent Greek word.
καλό
"Καλό" means "good" or "nice" in English.
The adjective "καλό" describes the quality of the book as being good or favorable.
Αυτό είναι ένα καλό βιβλίο.
This is a good book.
The adjective "καλή" modifies the noun "ημέρα" (day), conveying the intention of the day being positive or pleasant.
Καλημέρα! Ελπίζω να έχεις μια καλή ημέρα.
Good morning! I hope you have a good day.
The adjective "καλές" describes "στιγμές" (times), expressing that the times were enjoyable or memorable.