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

The SI unit for the dose equivalent of ionizing radiation. One sievert represents a dosage of 1 → joule per kg of tissue, absorbed from the ionizing radiation. The effect of radiation depends on its total amount of energy, the type of radiation, and the energy levels of particular particles. The dose equivalent in sieverts of radiation is the product of the absorbed dose in → gray (Gy)s and a dimensionless numeric factor, called the quality factor or relative biological effectiveness, dependent on the type of radiation. The sievert has replaced the → rem as the unit of dose equivalent. 1 rem = 10^-2 Sv.

The unit honors the Swedish physicist Rolf Sievert (1898-1966), who worked over many years to measure and standardize the radiation doses used in cancer treatment.

The act or fact of seeing; field of vision. → line of sight.

M.E., from O.E. gesiht, gesihð "thing seen;" cf. Dan. sigte, Swed. sigt, M.Du. sicht, Du. zicht, O.H.G. siht, Ger. Sicht, Gesicht, related to → sign.

Did "sight, vision," past stem of didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen").

→ line of sight.

→ sight; → line.

1) A conventional or arbitrary mark, figure, or symbol used as an abbreviation for the word or words it represents. Related terms: → signal, → signature, → symbol, → index.
2) Math.: A plus sign or minus sign used as a symbol for indicating addition or subtraction; also a sign for indicating the positive or negative value of a quantity.
3) → sign of the zodiac.

M.E., from O.Fr. signe "sign, mark, signature," from L. signum "mark, token, indication, symbol," from PIE base *sek^w- "to see."

Nešân "sign, mark," from Mid.Pers. nišân "sign, mark, omen," nišitan "to gaze, stare, look into," niš in marv.niš "taking omen, foretelling, or divining from birds," nišak "clear, evident," from Proto-Iranian *niiaš- "to show," from *ni- "down, below," → ni- (PIE), + *iaš- "to show, appear;" cf. Armenian loanword niš "sign, mark, spot," loaned also in Syriac as nyš "sign" (Cheung 2007).

One of the 12 constellations (in fact 13) making up the → zodiac.

→ sign; → zodiac.

Borj originally "tower," most probably related to Pers. borz "height, magnitude, greatness," boland "high," bâlâ "up, above, high, elevated, height," Laki dialect berg "hill, mountain;" Mid.Pers. burz "height," buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. and E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- "high." Borj may have been loaned into Ar. from Mid.Pers. The meaning extension of borj to its astronomical sense of zodiacal sign may have arisen from the conception of the zodiac as a barrier between heaven and Earth through which access was gained by means of twelve gates.

1) Useful part of the received information that can be distinguished from noise.
2) Information transmitted by means of a modulated current or an electromagnetic wave and received by telephone, radio, television, etc.

M.E., from O.Fr. signal, from M.L. signale "a signal," from L.L. signalis (adj.) "used as a signal, pertaining to a sign," from L. signum "signal, sign."

Nešâl, from neš- base of nešân meaning → sign + -âl, → -al.

Concept used to quantify the effects of noise. It is the ratio of a signal to the standard deviation of the signal.

→ signal; → noise; → ratio.

1) Physics, Chem.: A distinctive trace or sign that indicates the presence of a substance or the occurrence of a physical process or event.
2) Telecommunication: The complete set of electromagnetic and/or acoustic signals received, e.g., from an infrared source, a radio or radar transmitter, an aircraft, or a ship. Signatures may consist of analog or digital signals, or both, and may be analyzed to indicate the nature of their source and assist in its recognition.

M.Fr. signature, from M.L. signatura "sign," in classical L. "the matrix of a seal," from signatus, p.p. of signare "to mark, sign," → sign.

Nešânzad, literally "striking a mark, sign" (cf. angošt zadan "fingerprint"), from nešân, → sign, + zad past stem of zadan "to strike, beat; to do; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill").

1) The state or quality of being significant; → meaning; importance.
2) Statistics: An estimated measure of the degree to which a result is not merely a matter of chance. See also → significance level, → significance testing.

From L. significantia "meaning, force, energy," from significans, present participle of significare, → signify.

Nešânâri, noun from nešânâr, → significant.

The level of → Type I error which one is willing to risk in a → test of significance. Also called level of significance.

→ significance; → level.

Statistics: A procedure that is used to decide whether to accept or reject the → null hypothesis or to determine whether observed samples differ significantly from expected results. Also called → test of significance and → rule of decision.

→ significance; → test.

1) Having a special or suggestive → meaning.
2) Statistics: Of or pertaining to a result that is not plausible to occur by chance.

From L. significant-, stem of significans, from significare, "to → signify."

Nešânâr, from nešân, → sign, + âr short form of âvar present stem of âvardan "to bring, adduce, cause, produce."

The number of digits used to express a measured or calculated quantity. Rules for deciding the number of significant digits:
The leftmost digit which is not a zero is the most significant digit.
If the number does not have a decimal point, the rightmost digit which is not a zero is the least significant digit.
If the number does have a decimal point, the rightmost significant digit is the least significant digit, even if it's a zero.
Every digit between the least and most significant digits should be counted as a significant digit.

→ significant; → digit.

1) Something that is signified, → meaning, sense.
2) The act of signifying. → significance, → significant, → level of significance.

Verbal noun of → signify.

To make known; to be a sign of; to → mean. → significance, → significant, → signification.

M.E. signifien, from O.Fr. signifier, from L. significare "to make a sign, indicate, mention, denote."

Nešânâridan, from nešânâr, → significant, + -dan suffix of infinitives.

1) Absence of sound or noise.
2) The state or fact of being silent.

Noun from → silent.

1) Making no sound; quiet; still.
2) Refraining from speech.

From L. silentem (nominative silens) "still, calm, quiet," p.p. of silere "to be quiet or still," of unknown origin.

Bideng, from Kurd. (Kurmanji) bêdeng, bêdêng, Kurd. (Sorani) bedang, from bi- "without," → a-, + deng "sound, voice," variants dong, dang, bâng, → Big Bang.

A type of heat-resistant glass, especially in the form of flint or → quartz.

L. silex "hard stone, flint." Âtašzané "that used for kindling, ignitor," from âtaš, → fire, + zadan "to strike," → beat + -é instrument suffix. Caxmâq loan from Turkish.

A dark disk seen in absorption against the bright nebular background. → proplyd.

From Fr. silhouette, in allusion to Étienne de Silhouette (1709-67), Fr. controller general of finances in 1759; perhaps from his ephemeral tenure; → disk.

Gerdé, → disk; siyah-rox, from siyah, → black, + rox, variant of ru(y) "face, surface; aspect; appearance," (Mid.Pers. rôy, rôdh "face;" Av. raoδa- "growth," in plural form "appearance," from raod- "to grow, sprout, shoot;" cf. Skt. róha- "rising, height").

A widely found mineral of silicon dioxide SiO₂, which is used as an ore of → silicon. It is a hard, white, or colorless crystalline compound with a high melting point, occurring abundantly as quartz, sand, flint, rock crystal, etc.

From L. silic- stem of → silex "hard stone, flint, boulder."