For words that only have 3 letters, there isn't any 4th letter. As an example with the word “increase”, there isn't any much more letters Later on and therefore need to be the word "add". The word “addict” is during the BIP39 wordlist but you would have employed “addi” for https://topsocialplan.com/story4326073/little-known-facts-about-bip39-seed-phrase-list