A design or product specifications describe the characteristics of the solutions for the specification of the requirements and refers to either a solution designed or a ready e:m solution. It is often used to control manufacturing/production. Sometimes the term specification is used here in conjunction with a sheet (or data sheet), which can be confusing. A data sheet describes the technical characteristics of an article or product that is often published by a manufacturer to help people choose or use the products. A technical sheet is not a technical specification in the sense of information on how to produce it. In software development, a functional specification (including functional specifications or functional specifications or document functional specifications (FSDs) is the set of documentation describing the behavior of a computer program or a larger software system. The documentation usually describes different entries that can be made available to the software system and how the system reacts to those inputs. In some countries, word specification is mixed with word calendars. For example, in Serbia, cross-cutting plans have generally given specifications. On the other hand, “technical descriptions for the performance of works,” which must be considered specifications, are rarely referred to as “specifications” in the treaty. A design/product specification does not necessarily prove that a product is correct or useful in all contexts. An item can be checked to meet a specification or stamped with a specification number: this does not mean that the item is suitable for other unredified uses.
People who use the article (engineers, unions, etc.) or the article (building rules, government, industry, etc.) have a responsibility to take into account the choice of available specifications, to indicate the correct specifications, to impose compliance and to use the article correctly. Qualification validation is required. Specifications and other standards can be imposed outside, as described above, but also internal manufacturing and quality specifications. These exist not only for food or pharmaceutical products, but also for processing machines, quality processes, packaging, logistics (cold chain), etc. and are exemplary according to iso 14134 and ISO 15609.   A program specification is the definition of what is expected of a computer program. It may be informal, in which case it can be considered a manual of use from the developer`s point of view, or formally, in this case, it defined a particular meaning in mathematical or programmatic terms. In practice, many successful specifications are written to understand and optimize already well-developed applications, although critical security software systems are often carefully specified before the application is developed. Specifications are the most important for external interfaces that need to remain stable.
A specification often refers to a set of documented requirements that must be met by a material, design, product or service.  A specification is often a kind of technical standard.