IPA: /ˈrɒtənə/
KK: /ˈrɑtənər/
More decayed or spoiled than something else.
The fruit in the basket is rottener than the one on the table.
Comparative: rottener
Superlative: rottentest
Rottener → It is formed from "rotten" (from Old English *rotian*, meaning to decay or decompose) and "-er" (meaning one who or that which). The word "rottener" refers to something that is more decayed or decomposed than something else.
Think of something that is 'decaying' ('rotten') and the '-er' indicating it is 'more' of that state. This helps you remember that 'rottener' means more decayed.