An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

If event A must occur for event B to occur, then it is said that A is → necessary for B. If event A may cause B but there could be some other cause as well, then it is said that A is sufficient to cause B. See also → if and only if (iff).

→ necessary; → and; → sufficient; → condition.

Logic: A → proposition if its → denial is self-contradictory. Also called "logical truth" and "non-contingent truth."

→ necessary; → truth.

1) The fact of being necessary or indispensable.
2) Something necessary or indispensable.

→ necessary; → -ity.

The part of a person's or animal's → body that connecting the → head to the rest of the body.

M.E. nekke, from O.E. hnecca, cognate with Du. nek "the nape of the neck;" Ger. Nacken, O.Norse hnakki "the nape of the neck."

Gardan "neck;" related to geri, geribân "collar," gerivé "low hill," galu "throat;" Mid.Pers. gartan "neck," galôg, griv "throat;" Av. grīvā- "neck;" cf. Skt. gala- "throat, neck;" Gk. bora "food;" L. gula "throat" (Fr. gueule "(animal) mouth"), gluttire "to gulp down," vorare "to devour;" PIE base *g^wer- "to swallow, devour." L. gula; cf. Mod.Pers. galu "throat."

A slender pointed piece of metal, usually steel. → magnetic needle.

M.E. nedle, O.E. naeðlæ, nedlæ (cf. O.S. nathla, O.N. nal, O.Fris. nedle, O.H.G. nadala, Ger. Nadel); PIE root *(s)ne- "to sew, to spin;" cf. Skt. snayati "wraps up;" Gk. nein "to spin;" L. nere "to spin."

Suzan, Mid.Pers. sôzan, sucan, related to sok "pointed stick for driving cattle;" Av. sūkā- "needle;" cf. Skt. sūcī- "sting;" L. cuneus "wedge;" PIE base kū- "sharp; spike."

1) To deny the existence or truth of.
2) To cause to be ineffective or invalid.

From L. negatus p.p. of negare "to say 'no', deny," from Old L. nec "not," from PIE base *ne- "no, not."

Nâyidan infinitive from nâ "no, not," variants na, ni, ma- (prohitive); from Mid.Pers. nê, ma "no, not;" O.Pers. naiy, nai "not;" Av. nôit, naē "not;" cf. Skt. ná "not;" cf. L. ne-, in-, un-; Gk. ni; Lith. nè; O.C.S. ne "not;" PIE *ne-, as above.

1) The act of denying; → denial.
2) The absence or → opposite of something that is actual, positive, or affirmative.
3) A → negative statement, idea, doctrine; a contradiction, refutation, or rebuttal.
4) Logic: If p is a → proposition, then the statement "not p," denoted ¬ p, is the negation or opposite of p. If p is "It is sunny," then ¬ p is "It is not sunny." If p is → true, then ¬ p is → false, and vice versa.

Verbal noun of → negate.

1) General: Expressing, containing, or consisting of a negation, refusal, or denial.
2) Math.: Of or relating to a quantity less than zero. Of or relating to the sign (-).
3) Physics: Of or relating to an electric charge of the same sign as that of an electron.
4) Photography: Having dark for light and light for dark.
5) Opposite of → positive.
See also:
→ negative charge, → negative correlation, → negative crystal, → negative feedback, → negative lens, → negative number, → negative polarization, → negative pressure, → negative skewness.

From O.Fr. negatif (fem. negative), from L. negativus, "denying, inhibiting (legal actions); denied/refused; negative," from negare "to refuse, say 'no'" from Old L. nec "not", from Italic base *nek- "not," from PIE base *ne- "no, not."

Nâyidâr, from nâyidan, → negate, on the model of xaridâr, foruxtâr, xâstâr, virâstâr, etc.

An electric charge that has the same sign as the electron.

→ negative; → charge.

A correlation between two variables such that as one variable's values tend to increase, the other variable's values tend to decrease.

→ negative; → correlation.

A uniaxial, birefringent crystal in which the velocity of the extraordinary ray surpasses that of the ordinary ray.

→ negative; → crystal.

A → feedback process in which the → output reacts on the → input so as to reduce the initial → effect.

→ negative; → feedback.

Same as → divergent lens.

→ negative; → lens.

A → real number that is less than zero. A negative number is indicated by the → minus sign.

→ negative; → number.

A type of polarization in which the direction of polarization becomes reversed.

→ negative; → polarization.

A kind of pressure that contrarily to ordinary pressure pushes inward. In contrast with the → Newtonian mechanics, in → general relativity there are situations in which pressure can be negative. Positive pressure gives rise to attractive gravity, whereas negative pressure creates → repulsive gravity.

→ negative; → pressure.

Of a distribution function, a skewness in which the left tail (tail at small end of the distribution) is more pronounced that the right tail (tail at the large end of the distribution). → positive skewness.

→ negative; → skewness.

An obsolete term denoting a negatively charged electron, as opposed to a positron.

From → negative + → electron.

1) The area or region around or near some place or thing; vicinity. → solar neighborhood.
2) Math.: An → open set that contains a given point.

From neighbor, M.E., O.E. neahgebur, from neah→ near + -hood suffix denoting "state or condition of being;" M.E. -hode, -hod; O.E. -had "condition, position," cognate with Ger. -heit, Du. -heid.

Hamsâyegi, noun from hamsâyé "neighbor," literally "under, sharing the same shade," from ham-, → syn-, + sâyé, → shadow.

A period of → geologic time within the Cenozoic era, between 23 and 2.6 million years ago, which comprises the Miocene and Pliocene epochs.

From L. neo-, → new, + -gene, → gene.