Is a contract valid if it&#39;s in a language only the signatories speak?
<p>So, if it's either such an esoteric language that only the signatories speak it (say, a new variant of Esperanto, or an idioticon between twins)? Or if it were an archaic language- say, the two foremost professors of classical language in the world sign a contract written in a language which people technically know about, and can become experts in, but which essentially no one else has devoted the time and energy necessary to become  expert in?</p>

<p>(I ask because it is Friday in Iceland.)</p>

<p>The parties can be required under oath to explain what they understand the plain meaning of the words to be.</p>

<p>Where they disagree about the <em>plain meaning</em> of the words, they can use expert witnesses to give weight to their interpretation.</p>

<p>Once the judge determines the plain meaning of the words (either by agreement between the parties or by reference to expert witnesses or other evidence), it is a matter of standard <a href="https://law.stackexchange.com/questions/6236/how-are-contract-disputes-resolved/6237#6237">contract interpretation</a>.</p>

<p>Even in the case of an idioticon, where no expert witnesses are available, if the disagreement between the parties surrounds only a few words, the judge could find that there is no actual ambiguity because the context. Also, the judge could refer to parole evidence if needed.</p>

<hr>

<p>The purpose of the written contract is to provide evidence of your agreement. It is a bad idea to create evidence that you both may want to rely upon at some point if nobody else can understand it.</p>

united-states contract-law