The International Code of Nomenclature for algae, fungi, and plants (ICN or ICNafp) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "traditionally treated as algae, fungi, or plants".  : Preamble, para. 8 It was formerly called the International Code of Botanical Nomenclature (ICBN); the name was changed at the International Botanical Congress in Melbourne in July 2011 as part of the Melbourne Code  which replaced the Vienna Code of 2005.
The current version of the code is the Shenzhen Code adopted by the International Botanical Congress held in Shenzhen, China, in July 2017. As with previous codes, it took effect as soon as it was ratified by the congress (on 29 July 2017), but the documentation of the code in its final form was not published until 26 June 2018.
The name of the Code is partly capitalized and partly not. The lower-case for "algae, fungi, and plants" indicates that these terms are not formal names of clades, but indicate groups of organisms that were historically known by these names and traditionally studied by phycologists, mycologists, and botanists. This includes blue-green algae (Cyanobacteria); fungi, including chytrids, oomycetes, and slime moulds; photosynthetic protists and taxonomically related non-photosynthetic groups. There are special provisions in the ICN for some of these groups, as there are for fossils.
The ICN can only be changed by an International Botanical Congress (IBC), with the International Association for Plant Taxonomy providing the supporting infrastructure. Each new edition supersedes the earlier editions and is retroactive back to 1753, except where different starting dates are specified.  : Principle VI
For the naming of cultivated plants there is a separate code, the International Code of Nomenclature for Cultivated Plants , which gives rules and recommendations that supplement the ICN.
The rules governing botanical nomenclature have a long and tumultuous history, dating back to dissatisfaction with rules that were established in 1843 to govern zoological nomenclature.  The first set of international rules was the Lois de la nomenclature botanique ("Laws of botanical nomenclature") that was adopted as the "best guide to follow for botanical nomenclature"  at an "International Botanical Congress" convened in Paris in 1867.   Unlike modern Codes, it contained recommendations for naming to serve as the basis for discussions on the controversial points of nomenclature, rather than obligatory rules for validly published and legitimate names within the Code.  It was organized as six sections with 68 articles in total.
Multiple attempts to bring more "expedient" or more equitable practice to botanical nomenclature resulted in several competing codes, which finally reached a compromise with the 1930 congress.  In the meantime, the second edition of the international rules followed the Vienna congress in 1905. These rules were published as the Règles internationales de la Nomenclature botanique adoptées par le Congrès International de Botanique de Vienne 1905 (or in English, International rules of Botanical Nomenclature adopted by the International Botanical Conference of Vienna 1905). Informally they are referred to as the Vienna Rules (not to be confused with the Vienna Code of 2006).
Some but not all subsequent meetings of the International Botanical Congress have produced revised versions of these Rules, later called the International Code of Botanical Nomenclature, and then International Code of Nomenclature for algae, fungi, and plants.
The Nomenclature Section of the 18th International Botanical Congress in Melbourne, Australia (2011) made major changes:    
All the versions are listed below.
|Year of publication||Informal name|
|1867||Laws of botanical nomenclature|
|1883||Laws of botanical nomenclature, ed. 2|
|2000||St Louis Code|
|2018||Shenzhen Code (current)|
Specific to botany
Order is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families.
In biological classification, a subfamily is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoological names with "-inae".
In biology, a tribe is a taxonomic rank above genus, but below family and subfamily. It is sometimes subdivided into subtribes. By convention, all taxonomic ranks from genus upwards are capitalized, including both tribe and subtribe.
In biology, a type is a particular specimen of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes the defining features of that particular taxon. In older usage, a type was a taxon rather than a specimen.
A botanical name is a formal scientific name conforming to the International Code of Nomenclature for algae, fungi, and plants (ICN) and, if it concerns a plant cultigen, the additional cultivar or Group epithets must conform to the International Code of Nomenclature for Cultivated Plants (ICNCP). The code of nomenclature covers "all organisms traditionally treated as algae, fungi, or plants, whether fossil or non-fossil, including blue-green algae (Cyanobacteria), chytrids, oomycetes, slime moulds and photosynthetic protists with their taxonomically related non-photosynthetic groups ."
The International Association for Plant Taxonomy (IAPT) is an organization established to promote an understanding of plant biodiversity, facilitate international communication of research between botanists, and oversee matters of uniformity and stability in plant names. The IAPT was founded on July 18, 1950, at the Seventh International Botanical Congress in Stockholm, Sweden. The IAPT headquarters is located in Bratislava, Slovakia. Its president, since 2017, is Patrick S. Herendeen of the Chicago Botanic Garden; vice-president is Gonzalo Nieto Feliner of the Real Jardín Botánico, Madrid; and secretary-general is Karol Marhold of the Plant Science and Biodiversity Centre, Slovak Academy of Sciences, Bratislava.
Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical nomenclature is Linnaeus' Species Plantarum of 1753. Botanical nomenclature is governed by the International Code of Nomenclature for algae, fungi, and plants (ICN), which replaces the International Code of Botanical Nomenclature (ICBN). Fossil plants are also covered by the code of nomenclature.
Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms. To an end-user who only deals with names of species, with some awareness that species are assignable to families, it may not be noticeable that there is more than one code, but beyond this basic level these are rather different in the way they work.
In botany, the correct name according to the International Code of Nomenclature for algae, fungi, and plants (ICN) is the one and only botanical name that is to be used for a particular taxon, when that taxon has a particular circumscription, position and rank. Determining whether a name is correct is a complex procedure. The name must be validly published, a process which is defined in no less than 16 Articles of the ICN. It must also be "legitimate", which imposes some further requirements. If there are two or more legitimate names for the same taxon, then the correct name is the one which has priority, i.e. it was published earliest, although names may be conserved if they have been very widely used. Validly published names other than the correct name are called synonyms. Since taxonomists may disagree as to the circumscription, position or rank of a taxon, there can be more than one correct name for a particular plant. These may also be called synonyms.
International Botanical Congress (IBC) is an international meeting of botanists in all scientific fields, authorized by the International Association of Botanical and Mycological Societies (IABMS) and held every six years, with the location rotating between different continents. The current numbering system for the congresses starts from the year 1900; the XVIII IBC was held in Melbourne, Australia, 24–30 July 2011, and the XIX IBC was held in Shenzhen, China, 23–29 July 2017.
The International Code of Nomenclature for Cultivated Plants (ICNCP), is a guide to the rules and regulations for naming cultigens, plants whose origin or selection is primarily due to intentional human activity. It is also known as Cultivated Plant Code. Cultigens under the purview of the ICNCP include cultivars, Groups, and grexes. All organisms traditionally considered to be plants are included. Taxa that receive a name under the ICNCP will also be included within taxa named under the International Code of Nomenclature for algae, fungi, and plants, for example, a cultivar is a member of a species.
In botanical nomenclature, author citation is the way of citing the person or group of people who validly published a botanical name, i.e. who first published the name while fulfilling the formal requirements as specified by the International Code of Nomenclature for algae, fungi, and plants (ICN). In cases where a species is no longer in its original generic placement, both the authority for the original genus placement and that for the new combination are given.
Alphonse Louis Pierre Pyramusde Candolle was a French-Swiss botanist, the son of the Swiss botanist Augustin Pyramus de Candolle.
A conserved name or nomen conservandum is a scientific name that has specific nomenclatural protection. That is, the name is retained, even though it violates one or more rules which would otherwise prevent it from being legitimate. Nomen conservandum is a Latin term, meaning "a name to be conserved". The terms are often used interchangeably, such as by the International Code of Nomenclature for Algae, Fungi, and Plants (ICN), while the International Code of Zoological Nomenclature favours the term "conserved name".
In botanical nomenclature, autonyms are automatically created names, as regulated by the International Code of Nomenclature for algae, fungi, and plants that are created for certain subdivisions of genera and species, those that include the type of the genus or species. An autonym might not be mentioned in the publication that creates it as a side-effect. Autonyms "repeat unaltered" the genus name or species epithet of the taxon being subdivided, and no other name for that same subdivision is validly published. For example, Rubus subgenus Eubatus is not validly published, and the subgenus is known as Rubus subgen. Rubus.
Priority is a fundamental principle of modern botanical nomenclature and zoological nomenclature. Essentially, it is the principle of recognising the first valid application of a name to a plant or animal. There are two aspects to this:
Cultivated plant taxonomy is the study of the theory and practice of the science that identifies, describes, classifies, and names cultigens—those plants whose origin or selection is primarily due to intentional human activity. Cultivated plant taxonomists do, however, work with all kinds of plants in cultivation.
John Isaac Briquet was a Swiss botanist, director of the Conservatoire Botanique at Geneva.
The Kew Rule was used by some authors to determine the application of synonymous names in botanical nomenclature up to about 1906, but was and still is contrary to codes of botanical nomenclature including the International Code of Nomenclature for algae, fungi, and plants. Index Kewensis, a publication that aimed to list all botanical names for seed plants at the ranks of species and genus, used the Kew Rule until its Supplement IV was published in 1913.
Botanical Latin is a technical language based on New Latin, used for descriptions of botanical taxa. Until 2012, International Code of Botanical Nomenclature mandated Botanical Latin to be used for the descriptions of most new taxa. It is still the only language other than English accepted for descriptions. The names of organisms governed by the Code also have forms based on Latin.