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logic

(Encyclopedia)logic, the systematic study of valid inference. A distinction is drawn between logical validity and truth. Validity merely refers to formal properties of the process of inference. Thus, a conclusion w...

transuranium elements

(Encyclopedia)transuranium elements, in chemistry, radioactive elements with atomic numbers greater than that of uranium (at. no. 92). All the transuranium elements of the actinide series were discovered as synthet...

mechanics

(Encyclopedia)mechanics, branch of physics concerned with motion and the forces that tend to cause it; it includes study of the mechanical properties of matter, such as density, elasticity, and viscosity. Mechanics...

metallurgy

(Encyclopedia)metallurgy mĕtˈəlûrˌjē [key], science and technology of metals and their alloys. Modern metallurgical research is concerned with the preparation of radioactive metals, with obtaining metals econ...

relativity

(Encyclopedia)relativity, physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference. One consequ...

gravitation

(Encyclopedia)gravitation, the attractive force existing between any two particles of matter. The term gravitygravity is commonly used synonymously with gravitation, but in correct usage a definite distinction is...

petroleum

(Encyclopedia)petroleum, oily, flammable liquid that occurs naturally in deposits, usually beneath the surface of the earth; it is also called crude oil. It consists principally of a mixture of hydrocarbons, with t...

wool

(Encyclopedia)wool, fiber made from the fleece of the domestic sheep. In the United States, by the Wool Products Labeling Act of 1939, the term wool may be applied only to fabrics made entirely of new wool; t...

cell, in biology

(Encyclopedia)CE5 Animal cell cell, in biology, the unit of structure and function of which all plants and animals are composed. The cell is the smallest unit in the living organism that is capable of integrati...

molecule

(Encyclopedia)molecule mŏlˈəkyo͞ol [key] [New Lat.,=little mass], smallest particle of a compound that has all the chemical properties of that compound. A single atom is usually not referred to as a molecule, a...