run/bip-0039/bip-0039-wordlists.md
Developers implementing phrase generation or checksum verification must separate words using ideographic spaces / accommodate users inputting ideographic spaces. (UTF-8 bytes: 0xE38080; C/C+/Java: "\u3000"; Python: u"\u3000") However, code that only accepts Japanese phrases but does not generate or verify them should be fine as is. This is because when generating the seed, normalization as per the spec will automatically change the ideographic spaces into normal ASCII spaces, so as long as your code never shows the user an ASCII space separated phrase or tries to split the phrase input by the user, dealing with ASCII or Ideographic space is the same.
Word-wrapping doesn't work well, so making sure that words only word-wrap at one of the ideographic spaces may be a necessary step. As a long word split in two could be mistaken easily for two smaller words (This would be a problem with any of the 3 character sets in Japanese)
Words can be uniquely determined typing the first 4 characters (sometimes less).
Special Spanish characters like 'ñ', 'ü', 'á', etc... are considered equal to 'n', 'u', 'a', etc... in terms of identifying a word. Therefore, there is no need to use a Spanish keyboard to introduce the passphrase, an application with the Spanish wordlist will be able to identify the words after the first 4 chars have been typed even if the chars with accents have been replaced with the equivalent without accents.
There are no words in common between the Spanish wordlist and any other language wordlist, therefore it is possible to detect the language with just one word.
Credits: @Kirvx @NicolasDorier @ecdsa @EricLarch (The pull request)
Credits: @paoloaga @Polve
Words chosen using the following rules:
Rules 11 and 12 prevent the selection words that are not different enough. This makes each word more recognizable among others and less error prone. For example: the wordlist contains "atono", then "atomo" is rejected, but "atomico" is good.
All the words have been manually selected and automatically checked against the rules.