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Habituation to a specific practice, such as drinking alcoholic beverages or using drugs (for example, heroin, cocaine, or amphetamines), and disorders characterized by the chronic use of a drug, alcohol, or similar substance. Addiction and addictive…

A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

Any treatment or procedure that includes the in-vitro handling of oocytes (immature ova or egg cells) and sperm or embryos for the purpose of establishing a pregnancy. Assisted reproductive technology (ART) is undertaken as a treatment of…

Any of several leguminous plants, or their seeds, long utilized as food by humans or livestock. There are more than 40,000 varieties of beans, with only a small number of these being mass-produced for human or animal consumption. In particular,…

The common name for a malignant neoplasm or tumor. Cancer is a serious medical condition that develops when the orderly relationship of cell division and cell differentiation becomes disordered, leading to the development of neoplasms. Neoplasms are…

Cells within a tumor that possess the capacity to self-renew and cause the heterogeneous lineages of cancerous cells that comprise the tumor. Cancer stem cells (CSCs) typically represent a small percentage of all cells in a tumor (rarely more than…

Any member of the grass family (Poaceae or Gramineae) that produces edible grains usable as food by humans and livestock. Cereals are important cultivated crops. Common cereals include rice, wheat, barley, oats, maize (corn), sorghum, rye, and…

The administration of chemical substances for the treatment of disease, especially cancer, or for the prevention of aberrant growth of cells or tissues (neoplasms). In general, chemotherapy is the use of chemicals to treat any disease, but the term…

Any of a group of viruses that cause upper and lower respiratory tract diseases, gastroenteritis, hepatitis, and central nervous system infections in birds and mammals, including humans. Coronaviruses (Fig. 1) comprise a major group of common animal…

A genome-engineering technique that allows precise targeting of specific stretches of genetic code and editing of DNA at designated locations. The CRISPR/Cas9 system has been used as a general tool to engineer the genomes of many different…

The occurrence of cases of disease in excess of what is usually expected for a given period of time. An epidemic is a breakout of disease affecting unusually large numbers of people within a community or population. When an epidemic spreads…

The science, art, and practice of managing and using the natural resources that occur on and in association with forested lands. Forestry is the management of forested lands (see illustration). It involves the planning and implementation of…

Plants that have altered genetic material (DNA) through recombinant DNA (rDNA) manipulation. Genetic engineering of plants allows for very specific genetic changes to be made to a plant's deoxyribonucleic acid (DNA), as opposed to the random…

Commercially grown plants that have altered genetic material through artificial recombinant manipulation. Genetic modification is the latest scientific tool for developing improved crop varieties. Such genetically modified (GM) crops can help to…

An organism that has had its genetic material manipulated or altered in a laboratory setting through the use of genetic or genomic engineering techniques. Genetically modified organisms (GMOs) are microorganisms, plants, or animals that have been…

The artificial application of water to the soil to produce plant growth. Irrigation also cools the soil and atmosphere, making the environment favorable for plant growth. The use of some form of irrigation (Fig. 1) is well documented throughout the…

An emerging cancer therapy in which oncolytic viruses are used to target and destroy cancer cells without harming healthy cells. Oncolytic viruses (that is, viruses that destroy cancer cells, but not normal cells) are able to infect, replicate…

Any agent capable of causing disease. The term pathogen is usually restricted to living agents or microorganisms that produce disease. Pathogens are infectious and diverse, including bacteria (see illustration), viruses, rickettsia, fungi, yeasts,…

An annual leafy leguminous vine, Pisum sativum (order Fabales), cultivated for its smooth or wrinkled, round edible seeds, which are borne in dehiscent pods. The garden pea (Fig. 1) is one of the world's oldest cultivated crops. It is a native of…

The planning and implementation of actions to establish, protect, restore, and maintain trees and forests in cities and smaller communities. When the field of urban forestry began in the 1960s, it focused on individual trees along streets and…

A genus of Gram-negative, immotile and nonspore-forming, oval to rod-shaped, often pleomorphic bacteria that occur as parasites or pathogens in mammals (including humans), birds, and reptiles. Actinobacillus bacteria are facultatively aerobic,…

A bacterial genus in the family Vibrionaceae comprising oxidase-positive, facultatively anaerobic, monotrichously flagellated Gram-negative rods. The mesophilic species of Aeromonas are A. hydrophila, A. caviae, and A. sobria; the psychrophilic one…

A branch of meteorology that examines the effects and impacts of weather and climate on crops, rangeland, livestock, and various agricultural operations. Agricultural meteorology, or agrometeorology, addresses topics that often require an…

The pure and applied science that is concerned with botany and management of crop and ornamental plants for utilization by humankind. As it relates to plants, agricultural science concerns itself with the application of scientific methods to…

The art and science of crop and livestock production. In its broadest sense, agriculture comprises the entire range of technologies associated with the production of useful products from plants and animals, including soil cultivation, crop and…

The science and study of crops and soils. Agronomy is the umbrella term for a number of technical research and teaching activities (see illustration): crop physiology and management, soil science, plant breeding, and weed management frequently are…

Any of the organic compounds possessing one or more basic amino groups and one or more acidic carboxyl groups. Of the more than 80 amino acids that have been found in living organisms, approximately 20 serve as the building blocks for proteins.…

Any of a group of drugs of diverse chemical structure and physiological effects that are used for the relief of pain. Analgesics are drugs, including opiates, synthetic opioids, and salicylates, that are used primarily for pain relief (see…

A small infectious agent that is unable to replicate outside a living animal cell. Animal viruses infect animals and require animal cells as their host. Unlike other intracellular obligatory parasites (for example, chlamydiae and rickettsiae…

A chemical substance, produced by microorganisms, plants, marine organisms, and synthetically, that has the capacity in dilute solutions to inhibit the growth of bacteria or destroy bacteria. Antibiotics are important antibacterial agents. Most are…

The capability that a bacterium acquires to counteract an inhibitory chemical molecule or compound that was formerly effective in killing it or preventing its growth. Antibiotic resistance in bacteria (Fig. 1) is a hot topic in the media and in…

Chemical compounds biosynthetically or synthetically produced that destroy or usefully suppress the growth or metabolism of a variety of microscopic or submicroscopic forms of life. On the basis of their primary activity, antimicrobial agents (see…

A deciduous tree (genus Malus) in the order Rosales, which produces an edible, simple, fleshy, pome-type fruit. Apples (Fig. 1) belong to the family Rosaceae, which includes many other deciduous fruits, including pears, peaches, and cherries. There…

A group of diseases affecting joints or their component tissues. Arthritis is the collective term used to describe any joint disorder or process; it also typically involves inflammation. In common usage, arthritis often refers to any joint pain.…

Vegetables that are prevalent in Asian cuisines, but less well known in Western diets. Asian vegetables (Fig. 1), also referred to as Asian greens or oriental vegetables, are very important in Asian countries, but are not as popular in North America…

A nonsteroidal anti-inflammatory drug used to control pain, fever, and inflammation. Aspirin is one of the most prevalent medicines in the world and is used to reduce fever and treat minor aches, pains, and inflammation. Furthermore, it is the only…

The most common type of arrhythmia (any disorder of the heart rate or rhythm). Atrial fibrillation, often abbreviated AFib or AF, is a heart condition that can lead to potentially serious complications. It is associated with decreased quality of…

The study of bacteria. The science of bacteriology is a specialized branch of microbiology concerned with bacteria (Fig. 1). Although bacteria are different in some important respects from all other kinds of cells, their basic processes of…

A large tropical plant of the genus Musa and its edible fruit. The banana belongs to the family Musaceae (order Zingiberales). The banana of commerce (Musa acuminata), which is believed to have originated in the Asian tropics, was one of the…

The management and maintenance of colonies of honeybees for human purposes. Beekeeping is an ancient art. Although the commonly known honeybee species (Fig. 1) is native to Europe and Africa, humans have transported them to other continents. The…

The study of behavior change in response to drugs, chemicals, or other environmental conditions or agents. Behavioral toxicology investigates the effect of toxic exposure on organismal behavior. The toxic exposure can involve various chemicals,…

The use of parasitoids, predators, and pathogens to reduce injurious pest insect populations and consequently the damage that they cause. Biological insect control (or insect biocontrol) is the regulation of insect populations by biological means.…

The application of principles from applied and physical sciences to problems in healthcare and biology. As a field, biomedical engineering draws from a variety of disciplines including mechanical, chemical, electrical, and computer engineering, as…

A form of terrorism in which there is the intentional release of biological agents (viruses, bacteria, fungi, or toxins) from living organisms or agents in order to cause death or disease in humans, animals, and/or plants; also referred to as…

The practice of fertility control, including contraception, which is intended to prevent pregnancy, and the means of interrupting early pregnancy. The efficacy of the various methods of birth control and their consistency of use vary widely (see…

A genus of pathogenic gram-negative bacteria that are coccobacilli and obligate aerobes, and fail to ferment carbohydrates. Bordetella bacteria are respiratory pathogens. Bordetella pertussis, B. parapertussis, and B. bronchiseptica share greater…

The reaction that occurs when tissue (usually skin) receives more energy (heat, chemical energy, electrical energy, or radiation) than it can absorb without injury. Factors such as the duration of contact, temperature, volume of chemical, and…

A genus comprising yeasts that cause a variety of human diseases referred to as candidiasis. All Candida species are single-celled yeasts (fungal organisms) that are ovoid in shape and 3–5 μm in size, and they multiply by a process called budding.…

Any of the group of organic compounds consisting of carbon, hydrogen, and oxygen that includes sugars, starches, and cellulose. Carbohydrate compounds consist of carbon, hydrogen, and oxygen, with the general chemical formula Cm(H2O)n [Fig. 1]; the…

A biennial umbellifer (Daucus carota) of Asiatic and Mediterranean origin belonging to the plant order Apiales. The carrot (Daucus carota; Fig. 1) is grown for its edible roots, which are eaten raw or cooked. Cultivated forms of the root vegetable…

An autoimmune disorder caused by gluten sensitivity that damages the small intestine and leads to the malabsorption of nutrients from food. Celiac disease (CD) is an autoimmune condition of the small intestine that is believed to be T-cell…

A severe diarrheal disease caused by infection of the small bowel of humans with Vibrio cholerae. Cholera is an acute, infectious bacterial disease that results in serious, often fatal, gastrointestinal illness in humans. The causative agent is…

A contagious, fatal, neurological disease affecting members of the deer family. Chronic wasting disease (CWD) is a serious transmissible spongiform encephalopathy (prion disease) that affects cervids [members of the ruminant family Cervidae…

A group of trees belonging to the madder family (Rubiaceae), occurring indigenously in the cool, cloud forests of the Andes from Colombia to Peru. Many species of cinchona (genus Cinchona) have been described. Most are variants of C. pubescens (see…

A genus of bacteria, including a number of important human pathogens, comprising large anaerobic spore-forming rods that usually stain Gram-positive. Most species of the genus Clostridium are anaerobes, but a few will grow minimally in air at…

Mild traumatic brain injury resulting from externally inflicted trauma. Although concussion, or mild traumatic brain injury (TBI), has many symptoms, there is often no physical evidence of damage to the brain (see illustration). In most cases, a…

Structural abnormalities of the body that develop during embryogenesis and the fetal period; also called birth defects. Children with significant birth defects need more medical care than other children do, require more frequent hospitalizations,…

The treatment of acute, life-threatening disorders, usually in intensive care units. Critical care medicine has been practiced informally for many decades in trauma centers, postanesthesia recovery rooms, coronary care units, delivery rooms,…

A common asymptomatic invasion of the body by the cytomegalovirus, which can produce life-threatening illness in the immature fetus and in immunologically deficient subjects. Although asymptomatic in most individuals, cytomegalovirus (CMV) infection…

Equipment used in the production and processing of milk and milk products, including milking machines, cream separators, coolers, pasteurizers, homogenizers, butter-making equipment, evaporators and dryers, and related items of equipment. Dairy…

A general term for a genus of tall forage grasses, of which the most important species is the deeply rooted perennial Paspalum dilatatum. Dallis grass (see illustration) is widely grown in the southern United States, mostly for pasture, and remains…

Common name for the plant Colocasia esculenta, including the variety antiquorum (taro). Dasheen plants are among the few edible members of the aroid family (Araceae). Native to southeastern Asia and Malaysia, the plants supply local inhabitants with…

The date palm, Phoenix dactylifera, which is one of the oldest cultivated tree crops. The date palm provides a staple food for many populations in the Middle East and North Africa and is also highly valued for feed, fiber, and shelter. Beginning in…

Cessation of life functions. Death is the permanent termination of all vital cellular and body functions. It can involve the whole organism (somatic death), individual organs (organ death), individual cells (cellular death), and individual parts of…

Defoliants are chemicals that cause leaves to drop from plants; defoliation facilitates harvesting. Desiccants are chemicals that kill leaves of plants; the leaves may either drop off or remain attached; in the harvesting process the leaves are…

The division of forestry concerned with taxonomy of trees and other woody plants. The term dendrology is derived from the Ancient Greek: dendron (= tree) and -logia (= study of or science of); the term xylology is used occasionally to denote the…

A disease in which the mineralized tissues of the tooth undergo progressive destruction from the outside surface of the tooth. The scientific term of dental caries (Fig. 1) is more commonly referred to as tooth decay or cavities. Carious lesions…

The branch of biomedical science concerned with the embryology, development, and structure of the teeth, jaws, oral cavity, and adjacent structures, and with the prevention, diagnosis, and treatment of their abnormalities. The practice of general…

A genus of tropical shrubs belonging to the legume family [Leguminosae (Fabaceae)]. Plants of the genus Derris (see illustration), with their long branches climbing over other vegetation, occur as members of the jungle undergrowth in Southeast Asia,…

The process of identifying the presence of viruses that cause respiratory ailments. The detection of respiratory viruses greatly concerns epidemiologists and physicians. Acute respiratory diseases account for an estimated 75% of all acute…

A large group of flukes (parasitic flatworms) within the class Trematoda, with some thousands of described and probably many thousands of not yet described species. The Digenea range from about 0.2 mm (0.008 in.) to over 1 m (3.3 ft) in length. They…

A genus of the plantain family (Plantaginaceae) or figwort family (Scrophulariaceae), whose dried leaves contain a number of glucosides that can be used as powerful cardiac stimulants and diuretics. The genus Digitalis ranges from the Canary Islands…

An annual culinary herb, genus Anethum, of the carrot family, Apiaceae (Umbelliferae). Dill supplies four products: dill seed oil, dill leaf oil, dill seed, and dill leaf. Although all dill grown in the United States is one species, Anethum…

A deleterious set of responses which occurs at the subcellular level, stimulated by some injury, and which is often manifested in altered structure or functioning of the affected organism. The concept of disease has been changing as understanding of…

Any of the tree or shrub species in the genus Cornus. The tree, Cornus florida, also known as the flowering dogwood, may reach a height of 40 ft (12 m) and is found in the eastern half of the United States and in southern Ontario, Canada. It has…

A large coniferous tree, Pseudotsuga menziesii (formerly, P. taxifolia), known also as red fir, belonging to the pine family (Pinaceae). Douglas-fir is one of the most widespread and most valuable tree species of western North America and ranks…

Systems that deliver controlled amounts of a therapeutic agent over a prolonged period or in a desirable temporal fashion, thereby maintaining required plasma or tissue drug levels. Drug delivery systems are bioengineered mechanisms or devices used…

The ability of an organism to resist the action of an inhibitory molecule or compound. Drug resistance is the decreased reactivity of living organisms to the injurious actions of certain drugs and chemicals. Examples of drug resistance include…

Any tree of the genus Diospyros of the ebony family, containing more than 250 species. Some species of ebony are important for their succulent fruits, such as date plum, kaki plum, and persimmon, and several are important for timber, particularly…

A member type belonging to the genus Enterovirus in the Picornaviridae viral family. The name echovirus is derived from the term enteric cytopathogenic human orphan virus. Dozens of echovirus antigenic types exist. Only certain types have been…

The study of insects that have a direct influence on humanity. Though this includes beneficial as well as harmful species, most attention is devoted to the latter and how they become pests and are controlled. The emphasis on managing harmful insects…

This term is used chiefly to characterize the potency of a drug by the amount required to produce a response in 50% of the subjects to whom the drug is given. The term is also known as ED50 or median effective dose. At one time it was usual to try…

A warm-season vegetable (Solanum melongena) of Asiatic origin belonging to the plant order Solanales (formerly Polemoniales). Eggplant is grown for its usually egg-shaped flesh fruit (see illustration), which is eaten as a cooked vegetable. Cultural…

A tick-borne infection that often is asymptomatic but also can produce an illness ranging from a few mild symptoms to an overwhelming multisystem disease. Ehrlichiosis is included with those infections that are said to be emerging, either because…

Diagnosis employing equipment that can be used clinically to measure the intrinsic electrical activity of the heart (electrocardiography), the brain (electroencephalography), peripheral nerves (nerve conduction), and skeletal muscles…

The detection and recording of electrical activity generated by muscle fibers. The basic elements of motor control in the body are the motor units which comprise motor neurons in the brainstem or spinal cord, their axons, and from ten to several…

The use of electric current to treat disease. Electrotherapy is based on principles developed during the nineteenth and twentieth centuries following the first demonstration of “animal electricity” by Luigi Galvani in the eighteenth century. This…

Any species of Ulmus, a genus of hardwood trees in the Northern Hemisphere, with simple, serrate, deciduous leaves. The American or white elm (U. americana) is the most important species (Fig. 1). It is a large, typically vase-shaped tree that…

A genus of the viral family Picornaviridae. Members of the genus Enterovirus, that is, enteroviruses, include the polioviruses, coxsackieviruses, echoviruses, and rhinoviruses. They are small (17–28 nanometers in diameter), contain ribonucleic acid…

Prevention of an enzymatic process as a result of the interaction of some substance with the enzyme so as to decrease the rate of reaction. Enzymes, which are usually protein macromolecules, catalyze nearly all of the metabolic reactions in cells.…

A genus of low, leafless, green-stemmed shrubs belonging to the order Ephedrales, and the source of the drug ephedrine. Plant members of the Ephedra genus grow in dry, alkaline soils around the world. In the southwestern United States, these plants…

Ergot is the seedlike body of fungi (molds) of the genus Claviceps; ergotism is a complex disease of humans and certain domestic animals caused by ingestion of grains and cereals infested with ergot. Ingestion of these long, hard, purplish-black…

A genus of Gram-positive bacteria. The most notable species of the bacterial genus Erysipelothrix is E. rhusiopathiae. It is pathogenic and causes disease in a variety of animal species, including humans. Erysipelothrix rhusiopathiae is a rod-shaped…

A genus of facultatively anaerobic bacteria belonging to the family Enterobacteriaceae. Escherichia bacteria are named for Theodor Escherich, an Austrian pediatrician and bacteriologist, who first described these organisms in 1885. There are five…

A large and important Australian forest tree, including about 700 species in the family Myrtaceae. Eucalyptus trees (eucalypts; genus Eucalyptus) occur throughout Australia and are particularly prevalent in eastern areas of the continent. However,…

Viral diseases that occur only rarely in human populations of economically developed countries. Many exotic viral diseases (see illustration) cause significant human morbidity and mortality in less economically developed areas. Moreover, these…

Lenses worn to improve vision. The primary function of the eye is to focus light energy on the retina. In the optics of a normal eye, parallel rays of light are refracted into sharply focused points of light on the retina. Refraction is necessary…

A fatal disease of both domestic and exotic cats (particularly cheetahs) caused by feline infectious peritonitis virus, a member of the Coronaviridae family. There are multiple strains of the virus which vary in virulence. Feline infectious…

A type of cancer caused by the feline leukemia virus, a retrovirus which affects only a small percentage of freely roaming or domestic cats. The feline leukemia virus is genetically and morphologically similar to murine leukemia virus, from which it…

An acute virus infection of cats, also called feline viral enteritis and (erroneously) feline distemper. The virus infects all members of the cat family (Felidae) as well as some mink, ferrets, and skunks (Mustelidae); raccoons and coatimundi…