Nominal numbers are numbers used for identification only. They do not indicate quantity, rank, or any other measurement. However they may encode information. The properties of nominal numbers are the minimum required to refer to an entity as a number.
Examples of nominal numbers include; sport jersey numbers; telephone numbers; zip codes; transportation route numbers; etc.
Operations with nominal numbers
A Nominal number is a numeral, or a string of numerals that is used for identification only, so that the only valid operation that may be carried out with nominal numbers is comparison. That is, two or more nominal numbers can be compared to determine if they are identical; while this may seem trite, it is a distinction important for computer science.
The converse of this is that any other mathematical operation done with or upon nominal numbers yields nonsense. The pseudo-science of numerology rejects this, instead declaring the opposite as a fundamental tenet.
The number of threads per inch in the taper section is in a range between the nominal values of the cylindrical thread section and of an NPT thread with the same size.
The number of threads per inch in the axial direction in the case of the cylindrical thread section 1 is in accordance with the associated thread nominal size, that is to say in the present case 19 threads per inch.
The number of threads per inch of the taper thread section 2 is in a range between the nominal value for the cylindrical thread section 1 and the nominal value for the NPT with the same nominal thread size.
The properties of nominalnumbers are the minimum required to refer to an entity as a number.
The term "nominalnumber" is quite recent, and appears to have originated as a usage in school textbooks derived from the statistical term "nominal data", defined as data indicating "...[m]erely statements of qualitative category of membership."
Sport jersey numbers may be a true example of nominalnumbers, but it is difficult to tell whether they truly are, since it is in general unclear what policies are used by clubs to allocate them.
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