For words that have only 3 letters, there isn't any 4th letter. Such as with the word “increase”, there aren't any more letters afterwards and therefore need to be the word "add". The word “addict” is inside the BIP39 wordlist but you would've used “addi” for “addict”. You signed in https://bookmarkprobe.com/story19167791/not-known-facts-about-bip39-english-words