For words that have only 3 letters, there is no 4th letter. Such as with the word “incorporate”, there are no additional letters Later on and so have to be the word "include". The word “addict” is from the BIP39 wordlist but you might have made use of “addi” for https://myeasybookmarks.com/story4320408/facts-about-bip39-seed-phrase-word-list-revealed