This is the 12393rd most frequent Russian word.
картофельный
Potato-related.
'Картофельный' in this sentence is an adjective describing the type of soup: potato soup.
Он приготовил картофельный суп.
He cooked a potato soup.
'Картофельные' here is plural and describes the patties as being made primarily from potatoes.
Картофельные зразы были очень вкусными.
Potato patties were very tasty.
'Картофельную' is a feminine singular adjective here, describing the type of flour: potato flour.