Vagueness is a systematic phenomenon in natural languages. It is common and frequent, and it manifests in words such as: "big", "red", "heap", "many", etc. These terms have borderline cases, because for some objects we can’t say whether or not they fall within the extension of these concepts. The wave is a logical and philosophical challenge. Because, for a statement, the application of a vague term to an object of the borderline case produces an apparent indeterminacy of the truth value of the statement. This leads to the study of sorite, a resistant paradox that reflects the logical relationships inherent in vague terms. Nevertheless, it also turns out that the observational terms are vague, and that it is possible to apply sorite to the ...