Untranslatability is the property of text or speech for which no equivalent can be found when translated into another language. A text that is considered to be untranslatable is considered a lacuna, or lexical gap. The term arises when describing the difficulty of achieving the so-called perfect translation. It is based on the notion that there are certain concepts and words that are so interrelated that an accurate translation becomes an impossible task. Some writers have suggested that language carries sacred notions or is intrinsic to national identity. Brian James Baer posits that untranslatability is sometimes seen by nations as proof of the national genius. He quotes Alexandra Jaffe: "When translators talk about untranslatable, they often reinforce the notion that each language has its own 'genius', an 'essence' that naturally sets it apart from all other languages and reflects something of the 'soul' of its culture or people".

A translator, however, can resort to various translation procedures to compensate for a lexical gap. From this perspective, untranslatability does not carry deep linguistic relativity implications. Meaning can virtually always be translated, if not always with technical accuracy.