You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Translation

Context:
Comparison of a back-translation with the original text is sometimes used as a check on the accuracy of the original translation, much as the accuracy of a mathematical operation is sometimes checked by reversing the operation. But the results of such reverse-translation operations, while useful as approximate checks, are not always precisely reliable. Back-translation must in general be less accurate than back-calculation because linguistic symbols (words) are often ambiguous, whereas mathematical symbols are intentionally unequivocal.

Question:
What symbol set has the property of being intentionally unequivocal?

mathematical