A really simple but effective method to create an unintelligble language from a given language is applying a substitution cipher to the vocabulary. In order to be pronouncable, vowels should be substituted with vowels, and consonants with other consonant of comparable sonority.

It is of course a special case of a relexification, but is there a specific term for this?

  • 1
    "Substitution cipher" would be an appropriate term. Sep 20, 2018 at 8:28

3 Answers 3


"code" or "coded language". Probably mostly used in conjunction with sign languages, where the signs replace the (spoken) words (e.g. Signing Exact English as opposed to "natural" signed languages), but also for "encoded" spoken languages (either by relexification or phoneme substitution).

  • 1
    There is no need to put scare quotes around "natural." Sign languages like ASL ARE natural languages. Oct 7, 2018 at 17:39

I think we could use some terms from physics here. Let's say a relex is isochor (alternative: isomek from Ancient Greek mêkos "length") if it preserves length of words, and isotonic (alternative: isoson/isosonor/isosonic, a Latin-Greek mix) if it preserves sonority patterns. Your substitution cipher would then be an isochor-isotonic relexification.

  • But is it really a relexification? It's an encoding, not a different language. Oct 10, 2018 at 14:42
  • Relexification just means that the vocabulary of a language is changed to get a new language. And OP clearly wanted a new language, not only a cipher or encoding. ("method to create an unintelligble language", line 1)
    – Cecilia
    Oct 10, 2018 at 15:36

I have never heard of a "substitution cypher language."

One might adduce Pig Latin or Double Dutch as examples of such a thing, but these are not conlangs. They are typically called "language games." A substitution cypher is not a language--it's a way of disguising one or more languages.

To qualify as a conlang, a constructed communication system has to have its own grammar and its own way of mapping meanings onto words.

  • By those standards even Esperanto would at least be in question as a conlang either since its grammar is usually basically the same as English except for a few differences. Even though in reality it's flexible, in practice it's usually like English. I don't know where you draw the line between a game & a language but I don't think that's a good way to do it. Just because something doesn't have a completely original grammar doesn't mean it's not a language. I think that line is a lot blurrier than you're making it out to be.
    – jastako
    Apr 13, 2020 at 17:44
  • Esperanto's grammar may be similar to English in some ways, but as a whole, it is not English grammar. People who study Esperanto have to learn its grammar too, not just its words. // What is more, a "substitution cypher" is indifferent to the language it is used to encode. The same substitution cypher could be used to encrypt any number of languages. The same can't be said of Esperanto. // Bottom line: is "substitution cypher language" your own coinage, or can I look it up in linguistics articles? May 9, 2020 at 4:49
  • Esperanto Grammar is (in MOST cases) more like English than it is different. The main exception to that being that the plurality of nouns & adjectives has to match. Word order is the same in most cases. If grammar is what makes something a language, then I could take Pig Latin, change the word order & call it a language, right? I'm not sure I would agree that grammar alone makes a language.
    – jastako
    May 11, 2020 at 4:52
  • Having a grammar like that of English doesn't make Esperanto a substitution cypher. Consider "E-prime," English without the copula. The grammar is almost identical to English, but it is in no way a substitution cypher. BTW, you ignored the point that one substitution cypher can be used to encode any number of languages. Can Esperanto be used to send a message in Vietnamese, German, AND English? May 11, 2020 at 5:04
  • I never said that "grammar alone makes the language." I said that a properly constructed conlang would have its own grammar. You could call your code a language if you wanted to, but if your code strives for minimal deviation from a natural language, you'd be defeating the purpose of conlanging. It is supposed to be, at least, a creative endeavor. Your Pig Latin code is the conlanging equivalent of constructing a miniature golf course comprising one hole with a one-foot putt. You can do it, but don't expect golfers/conlangers to be impressed. May 11, 2020 at 5:12

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