For words that only have 3 letters, there is no 4th letter. Such as with the word “incorporate”, there are no much more letters Later on and therefore must be the word "insert". The word “addict” is in the BIP39 wordlist however, you would've employed “addi” for “addict”. An easy https://socialstrategie.com/story4490252/a-review-of-bip39-phrase-list