Retrospective generally means to take a look back at events that already have taken place. For example, the term is used in medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, describing a look back at a patient's medical history

Medical history

The medical history or anamnesis of a patient is information gained by a physician by asking specific questions, either of the patient or of other people who know the person and can give suitable information , with the aim of obtaining information useful in formulating a diagnosis and providing...

 or lifestyle.

Music

Retrospective compilations are sometimes assembled from an artist's greatest hits

Greatest hits

A greatest hits album is a music compilation album of successful, previously released songs by a particular artist or band...

.

Awards

A retrospective award is one which is created, and then awarded to all persons who would previously have received it. Alternatively, a slight change to the criteria of an existing award may result in retrospective awards being presented to persons who would have won the award under present rules. Comparatively few awards are presented retrospectively.

Software development

The term is also used in software engineering

Software engineering

Software Engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software, and the study of these approaches; that is, the application of engineering to software...

, where a retrospective is a meeting held by a project team at the end of a project or process (often after an iteration

Iterative and incremental development

Iterative and Incremental development is at the liver of a cyclic software development process developed in response to the weaknesses of the waterfall model...

) to discuss what was successful about the project or time period covered by that retrospective, what could be improved, and how to incorporate the successes and improvements in future iterations or projects.

In agile development

Agile software development

Agile software development is a group of software development methodologies based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams...

 retrospectives play a very important role in iterative and incremental development. At the end of every iteration a retrospective is held to look for ways to improve the process for the next iteration.

Law

The term is used in situations where the law is changed, making a previously committed lawful act now unlawful. Sir Stuart Bell

Stuart Bell

Sir Stuart Bell is a British Labour Party politician, who has been the Member of Parliament for Middlesbrough since 1983.-Early life:...

 used the term "retrospectivity" to describe the Thomas Legg

Thomas Legg

Sir Thomas Stuart Legg, KCB, QC , is a senior former British civil servant, who was Permanent Secretary of the Lord Chancellor's Department and Clerk of the Crown in Chancery, United Kingdom, 1989-1998.-Biography:...

 audit of MPs' expenses. Usually the terms ex post facto law

Ex post facto law

An ex post facto law or retroactive law is a law that retroactively changes the legal consequences of actions committed or relationships that existed prior to the enactment of the law...

 or retroactive law are used. An example for a retrospective or retroactive law in force is the International Code of Zoological Nomenclature

International Code of Zoological Nomenclature

The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

 (ICZN Code), a convention

Convention (norm)

A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....

 which governs the formal scientific naming

Binomial nomenclature

Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...

 of animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, of which the 4th edition is effective since 2000. All previous editions of the ICZN Code, or previous other rules and conventions have no force any more today, and the scientific names published back in these times are to be evaluated only under the present edition of the ICZN Code.