A specification is an official description of a valid potential element within a specific designed form.
Specifications are basic to diverse design contexts, and may be created by any agent for many reasons. Specifications are most often associated with components in physical systems. However, specifications may include responsibilities and roles in social contexts.
A specification must identify one or more important traits of the specified element. Specifications do not try to (impossibly) identify or define all potential traits of each instance of a specified element.
Specifications tend to focus upon required traits of each instance, and agents often intend for a specification to create a necessary and sufficient set of requirements.
Specifications also often identify recommended traits. They can also indicate prohibited and unwanted traits.
Specifications may identify positively or negatively defined requirements and recommendations. For example, a specification could indicate that a computer must use a specific type of power supply, and it may also indicate that that computer may not contain specific (possibly rare or dangerous) chemical compounds.
Many information resources are specifications, although they may rarely be perceived as such. In addition to the aforementioned basic specification types of requirement and recommendation, here are some concepts which inherently are specifications:
criterion, format, guideline, law, parameter, plan, protocol, qualification, recipe, rule
Standard: Mutually useful specifications often become unofficial or official standards.