For words that only have three letters, there's no 4th letter. Such as with the word “include”, there won't be any much more letters Later on and therefore needs to be the word "incorporate". The word “addict” is while in the BIP39 wordlist but you would've applied “addi” for “addict”. https://thebookmarklist.com/story18751904/bip39-seed-phrase-fundamentals-explained