A couple days ago I wrote about how you might go about trying to recover a seed phrase that you had remembered out of order. I said that the list of seed phrase words had been designed to be distinct. Just out of curiosity I computed how similar the words are using Levenshtein distance, also known as edit distance, the number of single character edits it takes to turn one word into another.
A lot of the words—484 out of 2048—on the BIP39 list differ from one or more other words by only a single character, such as angle & ankle, or loud & cloud. The word wine is one character away from each of wing, wink, wire, and wise.
Other kinds of similarity
Edit distance may not the best metric to use because it measures differences in text representation. It’s more important for words to be conceptually or phonetically distinct than to be distinct in their spelling. For example, the pair donkey & monkey differ by one letter but are phonetically and conceptually distinct, as are the words live & olive.
Some pairs of words are very similar phonetically. For example, I wouldn’t want to have to distinguish or cannon & canyon over a phone call. The list is not good for phonetic distinction, unlike say the NATO alphabet.
Memorization
For ease of memorization, you want words that are vivid and concrete, preferably nouns. That would rule out pairs like either & neither.
The BIP39 list of words is standard. But other approaches, such as Major system encoding, are more optimized for memorability.
Design
It’s hard to make a long list of words distinct by any criteria, and 2048 is a lot of words. And the words on the list are intended to be familiar to everyone. Adding more vivid or distinct words would risk including words that not everyone would know. But still, it seems like it might have been possible to create a better word list.
Recovery
The earlier post discussed how to recover a seed phrase assuming that all the words are correct but in the wrong order. It would make sense to explore sequences in order of permutation distance, assuming that small changes to the order are more likely than large changes.
But if it’s possible that the words are not correct, you might try looking at words in edit distance order. For example, “You said one of the words was race. Could it have been rice?”