For words that have only 3 letters, there is not any 4th letter. For example with the word “increase”, there isn't any far more letters afterwards and thus must be the word "include". The word “addict” is within the BIP39 wordlist but you would have made use of “addi” for https://bookmarkmoz.com/story18986985/bip39-seed-phrase-mnemonics-generator-an-overview