17-letter words containing o, n, e, a, c
- national cemetery — a cemetery, maintained by the U.S. government, for persons who have served honorably in the armed forces.
- national covenant — an agreement (1638) among Scottish Presbyterians to uphold their faith in Scotland.
- 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 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.
- near-earth object — a comet or asteroid pushed by the gravitational attraction of nearby planets into an orbit that allows it to enter the earth's orbit and thereby pose a danger of collision. Abbreviation: NEO.
- neo-scholasticism — a contemporary application of Scholasticism to modern problems and life.
- nephelometrically — By means of nephelometry.
- 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.
- never looked back — If you say that someone did something and then never looked back, you mean that they were very successful from that time on.
- new scotland yard — See under Scotland Yard (def 1).
- ninth commandment — “Thou shalt not bear false witness against thy neighbor”: ninth of the Ten Commandments.
- nitrogen narcosis — a semistupor, lightheadedness, or euphoria experienced by deep-sea divers when nitrogen from air enters the blood at higher than atmospheric pressure.
- non-certification — the act of certifying.
- non-communicative — inclined to communicate or impart; talkative: He isn't feeling very communicative today.
- non-consideration — the act of considering; careful thought; meditation; deliberation: I will give your project full consideration.
- non-containerized — to package (freight) in uniform, sealed containers for shipment.
- non-controversial — of, relating to, or characteristic of controversy, or prolonged public dispute, debate, or contention; polemical: a controversial book.
- non-discretionary — subject or left to one's own discretion.
- non-materialistic — excessively concerned with physical comforts or the acquisition of wealth and material possessions, rather than with spiritual, intellectual, or cultural values.
- non-reciprocating — to give, feel, etc., in return.
- non-retroactivity — operative with respect to past occurrences, as a statute; retrospective: a retroactive law.
- non-stereotypical — a process, now often replaced by more advanced methods, for making metal printing plates by taking a mold of composed type or the like in papier-mâché or other material and then taking from this mold a cast in type metal.
- non-thermoplastic — soft and pliable when heated, as some plastics, without any change of the inherent properties.
- nonaccomplishment — Something that does not achieve the intended goal.
- nonalcoholic beer — Nonalcoholic beer is beer that does not contain any alcohol.
- nonimpact printer — a printer that creates images without mechanically impacting the page, as an ink-jet or laser printer.
- nonteaching staff — employees within an academic or vocational environment whose jobs do not involve teaching
- north miami beach — a city in SE Florida.
- northern michigan — the peninsula between lakes Superior and Michigan constituting the N part of Michigan. Abbreviation: U.P.
- 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 mince matters — to speak frankly
- 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 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.
- 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
- objectionableness — The quality of being objectionable.
- occipital condyle — a protrusion on the occipital bone of the skull that forms a joint with the first cervical vertebra, enabling the head to move relative to the neck.
- ocean engineering — the branch of engineering that deals with the development of equipment and techniques for the exploration of the ocean floor and exploitation of its resources.
- oceanographically — In terms of oceanography.
- octadecanoic acid — stearic acid.
- off-year election — (in the US) an election held in a year when a presidential election does not take place