Children's, Intermediate and Advanced Online English Dictionary & Thesaurus

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ABO system a classification system for the inherited antigens found on the surface of human red blood cells, which determine compatibility for blood transfusions.
autonomic nervous system the part of the nervous system in vertebrates that controls involuntary bodily processes, such as the operation of the heart, stomach, and glands; sympathetic and parasympathetic nervous systems together.
Bertillon system a system used before the adoption of fingerprinting for identification, esp. of criminals, through records of bodily measurements, markings, coloring, and the like.
binary system a numbering system with a base of two. In binary numbers, any number can be expressed by 1, 0, or a combination of these. The number five is written as "101" in the binary system.
caste system a social structure in which one's class in society is determined by heredity.
circulatory system a system in the body made up of the heart, blood vessels, blood, and lymph vessels that carries blood and lymph around the body.
Copernican system the theory, first held by Copernicus, that the earth and other planets revolve around the sun.
decimal system a numbering or measuring system based on the number ten. [2 definitions]
digestive system the parts of the body that work together to break down food so that it can be used by the body as energy. The human digestive system includes the mouth, esophagus, stomach, and intestines.
honor system an arrangement wherein participants in a particular program, such as students in a school, are trusted to perform various tasks or duties without direct supervision.
immune system the bodily system of organs, tissues, cells, and cell products, which protects the body by detecting the presence of, and disabling, disease-causing agents in the body.
life-support system a system of equipment, esp. in a hospital, that keeps a person alive when he or she might otherwise die. [2 definitions]
limbic system a set of brain structures, located at the border (or limbus) separating the cerebral hemisphere from the brain stem, that support emotional responses, behavior, memory formation, and olfaction.
merit system a system in which people are hired or promoted to civil service positions on the basis of the results of competitive examinations.
metric system an international system of weights and measures based on the number ten, in which the basic units are the meter for length, the gram for weight, and the liter for volume.
nervous system the system of nerves and nerve centers in most multicellular animals.
operating system in computing, the software that controls and manages all aspects of a computer's operation, including the execution of application programs; the functioning of computer hardware; data input and output; the timing of and allocation of resources to the execution of multiple, simultaneous tasks; the physical storage and location of data; and computer security. Users interact with the operating system though a graphical user interface.
periodic system a system of classifying the chemical elements, based on the periodic law.
point system a method of grading that uses numbers instead of letter grades. [4 definitions]
Ptolemaic system the cosmographic theory, systematized by the Hellenistic astronomer Ptolemy, according to which all heavenly bodies revolve around the earth, which is fixed at the center of the universe.