A fundamental, essential, or irreducible constituent of a composite entity. The basic assumptions or principles of a subject. Mathematics A member of a set. Mathematics A point, line, or plane. Mathematics A part of a geometric configuration, such as an angle in a triangle. Mathematics The generatrix of a geometric figure. Mathematics Any of the terms in the rectangular array of terms that constitute a matrix or determinant. Chemistry & Physics A substance composed of atoms having an identical number of protons in each nucleus. Elements cannot be reduced to simpler substances by normal chemical means. One of four substances, earth, air, fire, or water, formerly regarded as a fundamental constituent of the universe. Electricity The resistance wire in an electrical appliance such as a heater or an oven. The forces that constitute the weather, especially severe or inclement weather: outside paint that had been damaged by the elements. An environment naturally suited to or associated with an individual: He is in his element when traveling. The business world is her element. A distinct group within a larger community: the dissident element on campus. A part of a military force, especially: A ground unit in an air force comparable to a platoon. A unit of an air force equal to two or three aircraft. The bread and wine of the Eucharist.