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17-letter words containing u, n, c, e, a

  • national security — defence of a country
  • natural deduction — (logic)   A set of rules expressing how valid proofs may be constructed in predicate logic. In the traditional notation, a horizontal line separates premises (above) from conclusions (below). Vertical ellipsis (dots) stand for a series of applications of the rules. "T" is the constant "true" and "F" is the constant "false" (sometimes written with a LaTeX \perp). "^" is the AND (conjunction) operator, "v" is the inclusive OR (disjunction) operator and "/" is NOT (negation or complement, normally written with a LaTeX \neg). P, Q, P1, P2, etc. stand for propositions such as "Socrates was a man". P[x] is a proposition possibly containing instances of the variable x, e.g. "x can fly". A proof (a sequence of applications of the rules) may be enclosed in a box. A boxed proof produces conclusions that are only valid given the assumptions made inside the box, however, the proof demonstrates certain relationships which are valid outside the box. For example, the box below labelled "Implication introduction" starts by assuming P, which need not be a true proposition so long as it can be used to derive Q. Truth introduction: - T (Truth is free). Binary AND introduction: ----------- | . | . | | . | . | | Q1 | Q2 | ----------- Q1 ^ Q2 (If we can derive both Q1 and Q2 then Q1^Q2 is true). N-ary AND introduction: ---------------- | . | .. | . | | . | .. | . | | Q1 | .. | Qn | ---------------- Q1^..^Qi^..^Qn Other n-ary rules follow the binary versions similarly. Quantified AND introduction: --------- | x . | | . | | Q[x] | --------- For all x . Q[x] (If we can prove Q for arbitrary x then Q is true for all x). Falsity elimination: F - Q (Falsity opens the floodgates). OR elimination: P1 v P2 ----------- | P1 | P2 | | . | . | | . | . | | Q | Q | ----------- Q (Given P1 v P2, if Q follows from both then Q is true). Exists elimination: Exists x . P[x] ----------- | x P[x] | | . | | . | | Q | ----------- Q (If Q follows from P[x] for arbitrary x and such an x exists then Q is true). OR introduction 1: P1 ------- P1 v P2 (If P1 is true then P1 OR anything is true). OR introduction 2: P2 ------- P1 v P2 (If P2 is true then anything OR P2 is true). Similar symmetries apply to ^ rules. Exists introduction: P[a] ------------- Exists x.P[x] (If P is true for "a" then it is true for all x). AND elimination 1: P1 ^ P2 ------- P1 (If P1 and P2 are true then P1 is true). For all elimination: For all x . P[x] ---------------- P[a] (If P is true for all x then it is true for "a"). For all implication introduction: ----------- | x P[x] | | . | | . | | Q[x] | ----------- For all x . P[x] -> Q[x] (If Q follows from P for arbitrary x then Q follows from P for all x). Implication introduction: ----- | P | | . | | . | | Q | ----- P -> Q (If Q follows from P then P implies Q). NOT introduction: ----- | P | | . | | . | | F | ----- / P (If falsity follows from P then P is false). NOT-NOT: //P --- P (If it is not the case that P is not true then P is true). For all implies exists: P[a] For all x . P[x] -> Q[x] ------------------------------- Q[a] (If P is true for given "a" and P implies Q for all x then Q is true for a). Implication elimination, modus ponens: P P -> Q ---------- Q (If P and P implies Q then Q). NOT elimination, contradiction: P /P ------ F (If P is true and P is not true then false is true).
  • natural frequency — the frequency at which a system vibrates when set in free vibration
  • natural resources — a naturally occurring source of wealth, as land or water.
  • natural selection — the process by which forms of life having traits that better enable them to adapt to specific environmental pressures, as predators, changes in climate, or competition for food or mates, will tend to survive and reproduce in greater numbers than others of their kind, thus ensuring the perpetuation of those favorable traits in succeeding generations.
  • natural-resources — a naturally occurring source of wealth, as land or water.
  • negative eugenics — the study of or belief in the possibility of improving the qualities of the human species or a human population, especially by such means as discouraging reproduction by persons having genetic defects or presumed to have inheritable undesirable traits (negative eugenics) or encouraging reproduction by persons presumed to have inheritable desirable traits (positive eugenics)
  • neurobiologically — In terms of or by means of neurobiology.
  • neuropathological — (medicine) Of, pertaining to, or arising from neuropathology, the pathology of nerve tissue.
  • neuropharmacology — the branch of pharmacology concerned with the effects of drugs on the nervous system.
  • neuropsychiatrist — A medical doctor specializing in neuropsychiatry; a medical doctor dealing with disorders that have both neurological and psychiatric features.
  • newspaper cutting — clipping from a news publication
  • nikita khrushchev — Nikita S(ergeyevich) [ni-kee-tuh sur-gey-uh-vich;; Russian nyi-kyee-tuh syir-gye-yuh-vyich] /nɪˈki tə sɜrˈgeɪ ə vɪtʃ;; Russian nyɪˈkyi tə syɪrˈgyɛ yə vyɪtʃ/ (Show IPA), 1894–1971, Russian political leader: premier of the U.S.S.R. 1958–64.
  • non-communicative — inclined to communicate or impart; talkative: He isn't feeling very communicative today.
  • norwegian current — an ocean current formed from the terminus of the North Atlantic Current, flowing N along the Norwegian coast into the Barents Sea.
  • nuclear chemistry — the branch of chemistry concerned with nuclear reactions
  • nuclear deterrent — a country's nuclear weapons viewed as a deterrent to other countries from attacking
  • nuclear isomerism — isomerism (def 2).
  • nuclear radiation — Physics. radiation in the form of elementary particles emitted by an atomic nucleus, as alpha rays or gamma rays, produced by decay of radioactive substances or by nuclear fission.
  • nuclear scientist — a scientist who studies nuclear physics
  • nuclear submarine — undersea vessel powered by atomic energy
  • nuclear threshold — the point in war at which a combatant brings nuclear weapons into use
  • nuclear-free zone — any area in which nuclear weapons, power plants, or materials are not allowed.
  • nuclear-isomerism — Chemistry. the relation of two or more compounds, radicals, or ions that are composed of the same kinds and numbers of atoms but differ from each other in structural arrangement (structural isomerism) as CH 3 OCH 3 and CH 3 CH 2 OH, or in the arrangement of their atoms in space and therefore in one or more properties. Compare optical isomerism, stereoisomerism.
  • numbering machine — a handheld device for stamping numbers onto objects
  • numerical control — control of a machine tool, or other device used in a manufacturing process, by a computer, other control circuitry, or recorded digital commands.
  • nursery education — education provided at a school for young children, usually from three to five years old
  • office automation — a method or system of using automated or electronic equipment, as word processors and computers, in the operations of an office.
  • olympic peninsula — a large peninsula of W Washington
  • organ-pipe cactus — a treelike or columnar cactus, Lemaireocereus marginatus, of Mexico, having a central, erect spine surrounded by spreading spines in clusters of five to eight, and funnel-shaped, brownish-purple flowers.
  • osculating circle — circle of curvature.
  • palace revolution — a challenge to or overthrow of a sovereign or other leader by members of the ruling family or group.
  • papanicolaou test — Pap test.
  • parachute payment — a payment made to alleviate hardship resulting from a sudden loss of income
  • per procurationem — by one acting as an agent; by proxy.
  • performance bonus — a monetary bonus paid to staff who have performed well in their job
  • performance drugs — the drugs that are taken illegally by athletes to enhance their sporting performance
  • permanent account — A permanent account is an account which carries its balance and is kept open from year to year.
  • pernicious anemia — Pernicious anemia is a very severe blood disease.
  • perpetual spinach — a variety of spinach that keeps producing edible leaves
  • personal computer — a compact computer that uses a microprocessor and is designed for individual use, as by a person in an office or at home or school, for such applications as word processing, data management, financial analysis, or computer games. Abbreviation: PC.
  • perspicaciousness — having keen mental perception and understanding; discerning: to exhibit perspicacious judgment.
  • phonological rule — an operation in generative phonology that substitutes one sound or class of sounds for another in a phonological derivation.
  • physical pendulum — any apparatus consisting of a body of possibly irregular shape allowed to rotate freely about a horizontal axis on which it is pivoted (distinguished from simple pendulum).
  • picture messaging — Picture messaging is the sending of photographs or pictures from one mobile phone to another.
  • pluvius insurance — insurance against rain
  • point of purchase — designating or in use at a retail outlet where an item can be purchased; point-of-sale: point-of-purchase displays to entice the buyer.
  • point-of-purchase — designating or in use at a retail outlet where an item can be purchased; point-of-sale: point-of-purchase displays to entice the buyer.
  • polymorphonuclear — (of a leukocyte) having a lobulate nucleus.
  • potassium cyanide — a white, granular, water-soluble, poisonous powder, KCN, having a faint almondlike odor, used chiefly in metallurgy and photography.
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