For words that only have three letters, there is not any 4th letter. As an example with the word “increase”, there aren't any much more letters afterwards and thus must be the word "incorporate". The word “addict” is during the BIP39 wordlist but you might have utilized “addi” for “addict”. https://7prbookmarks.com/story19052468/an-unbiased-view-of-bip39-seed-phrase-github