For words that only have 3 letters, there is no 4th letter. By way of example with the word “incorporate”, there aren't any extra letters Later on and so have to be the word "incorporate". The word “addict” is inside the BIP39 wordlist but you would've utilised “addi” for “addict”. https://classifylist.com/story20775608/top-latest-five-bip39-seed-phrase-mnemonics-generator-urban-news