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17-letter words containing r, o, t, u, n

  • 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 harmonics — harmonics of a note produced on a stringed instrument by lightly touching an open or unstopped sounded string.
  • natural logarithm — a logarithm having e as a base. Symbol: ln.
  • 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.
  • neurodegenerative — Resulting in or characterized by degeneration of the nervous system, especially the neurons in the brain.
  • neurofibromatosis — a dominantly inherited genetic disorder characterized by flat brown patches on the skin, neurofibromas of the skin and internal organs, and in some cases skeletal deformity.
  • neuropathological — (medicine) Of, pertaining to, or arising from neuropathology, the pathology of nerve tissue.
  • neurophysiologist — the branch of physiology dealing with the functions of the nervous system.
  • neuropsychiatrist — A medical doctor specializing in neuropsychiatry; a medical doctor dealing with disorders that have both neurological and psychiatric features.
  • neuropsychologist — A neurologist or psychologist whose speciality is neuropsychology.
  • neurotransmission — the transmission of a nerve impulse across a synapse.
  • neurotransmissive — Relating to neurotransmission.
  • neurotransmitters — Plural form of neurotransmitter.
  • non-argumentative — fond of or given to argument and dispute; disputatious; contentious: The law students were an unusually argumentative group.
  • non-authoritarian — favoring complete obedience or subjection to authority as opposed to individual freedom: authoritarian principles; authoritarian attitudes.
  • non-authoritative — having due authority; having the sanction or weight of authority: an authoritative opinion.
  • non-instructional — the act or practice of instructing or teaching; education.
  • non-reimbursement — to make repayment to for expense or loss incurred: The insurance company reimbursed him for his losses in the fire.
  • non-subordination — the act of placing in a lower rank or position: The refusal to allow women to be educated was part of society's subordination of women to men.
  • nonproductiveness — The quality of being nonproductive.
  • nonunderstandable — Not understandable.
  • northcountrywoman — a female native or inhabitant of the North of England
  • northern studfish — See under studfish.
  • norwegian current — an ocean current formed from the terminus of the North Atlantic Current, flowing N along the Norwegian coast into the Barents Sea.
  • not on your nelly — not under any circumstances; certainly not
  • notebook computer — laptop, portable
  • 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 threshold — the point in war at which a combatant brings nuclear weapons into use
  • number eight iron — a club with an iron head the face of which has more slope than a pitcher but less slope than a niblick.
  • number three wood — spoon (def 5).
  • 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
  • odds-on favourite — a person, team, horse, etc that is regarded as the most likely to win a competition
  • odour of sanctity — sanctimoniousness
  • oil of turpentine — a colorless, flammable, volatile essential oil having a penetrating odor and a pungent, bitter taste, obtained from turpentine oleoresin by distillation: used in paints and varnishes, and in medicine as a carminative, vermifuge, expectorant, rubefacient, and, formerly, as a diuretic.
  • old south arabian — a group of four closely related Semitic languages, having a writing system and used from about the eighth to the fifth centuries b.c. in the southern part of Arabia.
  • on (or off) duty — at (or temporarily relieved from) one's work, duty, etc.
  • on cruise control — If you say that someone is on cruise control in a contest, you mean that they are winning the contest easily and without needing to make a lot of effort.
  • on-the-job injury — On-the-job injury is bodily harm that is caused while you are doing your job.
  • opening arguments — the statements or arguments provided by lawyers at the beginning of a trial
  • opportunistically — adhering to a policy of opportunism; practicing opportunism.
  • 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.
  • out for the count — If someone is out for the count, they are unconscious or very deeply asleep.
  • out of all reason — unreasonable
  • out of proportion — exaggerated, excessive
  • outline agreement — a contract, etc, setting out the preliminary terms or guidelines for an agreement; a preliminary agreement
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