For words that only have three letters, there is no 4th letter. One example is with the word “incorporate”, there aren't any additional letters afterwards and therefore need to be the word "incorporate". The word “addict” is while in the BIP39 wordlist but you might have applied “addi” for “addict”. https://bookmarkeasier.com/story19002261/top-latest-five-bip39-seed-phrase-mnemonics-generator-urban-news