For words that have only 3 letters, there is no 4th letter. For example with the word “incorporate”, there won't be any much more letters afterwards and therefore has to be the word "increase". The word “addict” is within the BIP39 wordlist but you might have made use of “addi” https://redhotbookmarks.com/story18825210/not-known-facts-about-bip39-english-words