Explanatory Notes for the Medical Dictionary Names of Plants & Animals

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NAMES OF PLANTS & ANIMALS
The entries in this dictionary that define the names of plants and animals include common or vernacular names (as mosquito and poison ivy) and names from the formal, codified, New Latin vocabulary of biological systematics that denote categories at the level of the genus or higher. The vocabulary of biological nomenclature has been developed and used in accordance with international codes for the purpose of identifying and indicating the relationships of plants and animals. Organisms are classified into a hierarchy of groups--taxa--with each kind of organism having one--and only one--correct name and belonging to one--and only one--taxon at each level of classification in the hierarchy.

The fundamental taxon is the genus, which includes a group of closely related species of organisms and of which the name is a capitalized singular noun:

Ix.o.des . . . noun : a widespread genus of ixodid ticks (as the deer tick) many of which are bloodsucking parasites of humans and animals . . .

rhus . . . noun 1 capitalized : a genus of shrubs and trees of the cashew family (Anacardiaceae) that . . . include some (as poison ivy, poison oak, and poison sumac) producing irritating oils that cause dermatitis

Names of taxa higher than the genus (as family, order, class, and phylum) are capitalized plural nouns that are often used with singular verbs and that are not abbreviated in normal use:

Platy.hel.min.thes . . . noun plural : a phylum of ... usually much flattened invertebrates comprising the planarians, flukes, tapeworms, and related worms . . .

Trem.a.to.da . . . noun plural : a class of the phylum Platyhelminthes including the flukes and related parasitic flatworms . . .

The unique name of each kind of organism or species--the binomial or species name--consists of a singular capitalized genus name combined with an uncapitalized specific epithet. The name for a variety or subspecies--the trinomial, variety name, or subspecies name--adds a similar varietal or subspecific epithet. The head louse (Pediculus humanus capitis) is a subspecies of the species (Pediculus humanus) to which the body louse belongs.

If a name from biological nomenclature is used outside of parentheses as part of a definition in this dictionary, it appears as a vocabulary entry at its own place. If the name of a genus or higher taxon is used inside parentheses in a definition, it may or may not appear as an entry. Binomial, specific, subspecific, and varietal names do not usually appear as vocabulary entries (although common names derived from such names may be entered). In contrast, every common or vernacular name which is used in a definition whether inside or outside of parentheses is entered in this dictionary or in its companion volume, Merriam-Webster's Collegiate Dictionary.

Many common names are derived directly from the names of taxa and especially genera with little or no modification. The genus name (as Chlamydia or Giardia) is capitalized and italicized but never takes a plural. In contrast the common name (as chlamydia or giardia) is not usually capitalized or italicized but does take a plural (as chlamydiae or giardias). Occasionally, a common name in plural form (as coleoptera) may be spelled like the name of a taxon, but it is not usually capitalized. In many cases both the systematic taxonomic name and the common name derived from it are entered in this dictionary.

chla.myd.ia . . . noun 1 cap : the type genus of the family Chlamydiaceae comprising . . . 2 plural -i.ae . . . also -ias a : a bacterium of the genus Chlamydia . . .

giar.dia . . . noun 1 capitalized : a genus of flagellate protozoans inhabiting the intestines of various mammals and including one (G. lamblia syn. Lamblia intestinalis) that is associated with diarrhea in humans 2 : any flagellate of the genus Giardia

The entries defining the names of plants and animals are usually oriented to a taxon higher in the systematic hierarchy by a systematic name of higher rank (as Chlamydiaceae at Chlamydia), by a common name (as protozoan at Giardia or mosquito at Anopheles), or by a technical adjective (as digenetic at fluke or dipteran at mosquito) so that the systematic name of a higher, more inclusive taxon can usually be found by consulting another entry if it is not explicitly mentioned at the entry itself.

A genus name may be abbreviated to its initial letter when it is used as part of a binomial or trinomial name in the definition of the genus itself or when it is listed more than once in senses not separated by a boldface number.

A capitalized entry for a systematic taxonomic name of the form X n, synonym of Y or X noun plural, synonym of Y means that X has the same taxonomic rank and meaning as Y but that it is technically inferior to and less valid than Y. In a few cases a widely used synonym may be added after the currently recognized systematic name in some definitions:

Trichina . . . noun synonym of TRICHINELLA

plague . . . noun . . . 2 : a virulent contagious febrile disease that is caused by a bacterium of the genus Yersinia (Y. pestis syn. Pasteurella pestis)

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