For words that only have three letters, there is not any 4th letter. Such as with the word “insert”, there won't be any far more letters afterwards and thus must be the word "include". The word “addict” is in the BIP39 wordlist however, you would've applied “addi” for “addict”. Meticulously https://thesocialdelight.com/story4536133/the-greatest-guide-to-seed-phrase-bip39