This is the 513th most frequent Lithuanian word.
kokios
The Lithuanian word "kokios" translates to "what" or "which" (feminine plural form) in English.
In this instance, 'kokios' asks about a quality or type related to the plural feminine noun 'knygos' (books).
Kokios knygos tu mėgsti skaityti?
What kind of books do you like to read?
Here, 'kokios' refers to a specification of rules, matching the plural feminine noun 'taisyklės' (rules).
Kokios taisyklės galioja šioje vietoje?
What rules apply to this place?
Here, 'kokios' is used in a question about a specific characteristic (color) and agrees in gender and number with the noun 'spalvos' (colors).