dissatisfaction [dissatisfactions](unhappiness or discontent) noun [UK: ˌdɪs.ˌsæ.tɪs.ˈfæk.ʃn̩] [US: ˌdɪ.sæ.təs.ˈfæk.ʃn̩]I am writing to express my dissatisfaction. = Sto scrivendo per esprimere la mia insoddisfazione.
frustration [frustrations](feeling of annoyance) noun [UK: frʌ.ˈstreɪʃ.n̩] [US: frʌ.ˈstreɪʃ.n̩]