This is the 286th most frequent Slovenian word.
katerim
The Slovenian word "katerim" means "which" in the instrumental plural form.
In this sentence, 'katerim' serves as a relative pronoun in the dative plural, describing the books ('knjigah') and showing that the action of 'in which I trust' is applied to them.
V knjigah, katerim zaupam, je veliko koristnih informacij.
In the books in which I trust, there is a lot of useful information.
Here, 'katerim' is used as a relative pronoun in the dative plural, referring to 'zvezki' and expressing the notion of 'to which.'
Zvezki, katerim sem dodal platnice, so zdaj bolj vzdržljivi.
The notebooks to which I added covers are now more durable.
'Katerim' here acts as a relative pronoun in the dative plural, connecting 'predmeti' with the following explanation 'to which we dedicated the most attention.'