"Are you using a dictionary?"
We never use nominative after a verb, we use accusative or genitive. (And accusative can look like genitive (singular masculine animated, plural masculine personal), accusative (neuter, singular masculine not animated, plural not masculine personal), or have it's own distinct form (a -ending nouns)
list of most common verbs that require genitive is here https://www.duolingo.com/comment/16569658
As is said below (alik1989) używać takes / requires the genitive case. Słownik is masculine singular and inanimate and so (in genitive) would usually end "u" (not "a"). There are exceptions e.g words for tools, card games and dances (e.g młota = genitive for hammer). Is dictionary / słownik seen as a type of tool in this respect or is there another basis for słownik to be an exception?
Thank you Jellei. I was operating on the basis of the guidance in "Polish Grammar in a Nutshell" by Oscar E Swan as below. Inanimate masculine genitive seems to require a lot of intuition / guesswork.
Masculine Nouns 1. Genitive Sg. Animate nouns take Gsg. in -a. Most inanimates take Gsg. in -u. There are many exceptions and minor rules. For example, masculine-gender names for tools: młot --> młota (hammer), card games (poker --> pokera); dances: walc --> walca (waltz); months: listopad --> listopada (November); serially produced food items: pączek --> pączka (doughnut); and most Polish towns: Gdańsk --> Gdańska take –a. Among important exceptions are the words chleb --> chleba (bread), ser --> sera (cheese); compare miód --> miodu (honey) and szpital --> szpital (hospital); compare hotel --> hotelu (hotel).
There's no "używać się", I think ;) Unless you literally... use yourself for something?
Hmm. I see the logic in what you're saying, but "używać" (использовать) just needs Genitive. And actually использовать doesn't take Instrumental as well.
"posługiwać się" (this is my understanding of пользоваться) indeed takes Instrumental.