1. countable
There are countable and uncountable nouns.
Apple is a countable noun, so it makes grammatical sense to have five apples.
The trouble with "trouble" is that it's sometimes a verb, sometimes a noun, sometimes countable, sometimes not. Oh, well. Trouble troubles me little, and little troubles trouble me not at all.
Inglese parola "policzalne"(countable) si verifica in set:
50 lekcja z Rafałem - słownictwo angielsko-polskie...adam ludowa - 17