An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 82 Search : number
Abbe number
  عدد ِ آبه   
adad-e Abbe

Fr.: nombre d'Abbe   

The reciprocal of the → dispersive power of a substance. Also known as constringence.

Abbe sine condition; → number.

aberrational day number
  شماره‌ی ِ روز ِ بیراهشی   
šomâre-ye ruz-e birâheši

Fr.: nombre de jours d'aberration   

A → Besselian day number denoted by C or D.

aberration; → -al; → day; → number.

Alfvén Mach number
  عدد ِ ماخ ِ آلفونی   
adad-e Mach-e Alfvéni

Fr.: nombre de Mach alfvénique   

The ratio of the flow velocity to the → Alfvén speed in a medium.

Alfvén wave; → number.

Alfven Mach number
  عدد ِ ماخ ِ آلفونی   
adad-e Mach-e Alfvéni

Fr.: nombre de Mach alfvénique   

The ratio of the flow velocity to the → Alfvén speed in a medium.

Alfvén wave; → number.

algebraic number
  عدد ِ جبری   
adad-e jabri (#)

Fr.: nombre algébrique   

A number, → real or → complex, that is a → root of a → non-zero polynomial equation whose → coefficients are all → rational. For example, the root x of the polynomial x2 - 2x + 1 = 0 is an algebraic number, because the polynomial is non-zero and the coefficients are rational numbers. The imaginary number i is algebraic, because it is the solution to x2 + 1 = 0.

algebraic; → number.

atomic mass number (A-number)
  عدد ِ جرم ِ اتمی   
adad-e jerm-e atomi (#)

Fr.: nombre de masse atomique   

The total number of → protons and → neutrons in the → nucleus of an → atom (symbol A). For example, Oxygen-16 has a mass number of sixteen, because it has eight protons and eight neutrons.

atomic; → mass; → number.

atomic number
  عدد ِ اتمی   
adad-e atomi (#)

Fr.: nombre atomique   

The number of → protons in an → atomic nucleus (symbol Z). Same as → Z-number. The atomic number is written as a subscript to the left of the → chemical element name. For example, the most common isotope of oxygen is shown as 816O, which has 8 → protons and its → mass number (A) is 16.

atomic; → number.

Avogadro's number
  عدد ِ آووگادرو   
adad-e Avogâdro (#)

Fr.: nombre d'Avogadro   

Avogadro constant.

Named after Amedeo Avogadro (1776-1856), whose law allowed other physicists to calculate Avogadro's number; → constant.

azimuthal quantum number
  عدد ِ کو‌آنتومی ِ سوگانی   
adad-e kuântomi-ye sugâni

Fr.: nombre quantique azimutal   

In quantum mechanics, a quantum number that distinguishes the different shapes of the orbitals.

Azimuthal, adj. from → azimuth; → quantum number.

baryon number
  عدد ِ باریونی   
adad-e bâriyoni (#)

Fr.: nombre baryonique   

1) The difference between the total number of → baryons and the total number of → antibaryons in a system of → subatomic particles. It is a measure of → baryon asymmetry and is defined by the quantity η = (nb - nb-)/nγ, called the → baryon-photon ratio, where nb is the → comoving number density of baryons, nb- is the number of antibaryons, and nγ is that of photons. The value of η for the → cosmic microwave background radiation (CMBR) has been very well determined by the → WMAP satellite to be η = (6.14 ± 0.25) x 10-10. The baryon number is assumed to be constant. The photons created in stars amount to only a small fraction, less than 1%, of those in the CMBR.
2) A property of an → elementary particle represented by a → quantum number. It is equal to +1 for a baryon and -1 for an antibaryon. → Bosons, → leptons, and → mesons have a baryon number B = 0. → Quarks and → antiquarks have baryon numbers of B = +1/3 and -1/3, respectively. The baryon number is → conserved in all observed types of particle-particle interaction.

baryon; → number.

Besselian day number
  شماره‌ی ِ روز ِ بسلی   
šomâre-ye ruz-e Besseli


Any of the five quantities denoted by A, B, C, D, and E used in conjunction with → Besselian star constants for the reduction of a star's → mean catalog place to its → apparent place.

Besselian; → day; → number.

binary number system
  راژمان ِ عددهای ِ درینی   
râžmân-e adadhâ-ye dirini

Fr.: système des nombres binaires   

A → numeral system that has 2 as its base and uses only two digits, 0 and 1. The positional value of each digit in a binary number is twice the place value of the digit of its right side. Each binary digit is known as a bit. The decimal numbers from 0 to 10 are thus in binary 0, 1, 10, 11, 100, 101, 110, 111, 1000, 1001, and 1010. And, for example, the binary number 111012 represents the decimal number (1 × 24) + (1 × 23) + (1 × 22) + (0 × 21) + (1 × 20), or 29. In electronics, binary numbers are the flow of information in the form of zeros and ones used by computers. Computers use it to manipulate and store all of their data including numbers, words, videos, graphics, and music.

binary; → number; → system.

cardinal number
  عدد ِ اگرا   
adad-e agrâ

Fr.: nombre cardinal   

An ordinary number such as 0, 1, 2, or 3, as opposed to an → ordinal number such as 1st, 2nd, or 3rd. Cardinal numbers can be → zero or → positive and are used for counting the things that are assumed to be not divisible.

cardinal; → number.

complex number
  عدد ِ همتافت   
adad-e hamtâft (#)

Fr.: nombre complexe   

Any number of the form u = a + bi, where a and b are → real numbers and i imaginary, i.e. i2 = -1.

complex; → number.

composite number
  عدد ِ همنهاده   
adad-e hamnehâdé

Fr.: nombre composite   

A whole number which is the product of whole numbers other than itself and 1. The opposite of prime number. → compound number.

composite; → number.

compound number
  عدد ِ همنات   
adad-e hamnât

Fr.: nombre composé   

A quantity expressed as the sum of two or more quantities of differing units. For example 5 hours and 15 minutes or 4 meters and 20 centimeters. → composite number.

compound; → number.

congruent number
  عدد ِ دمساز   
adad-e damsâz

Fr.: nombre congru   

Number theory: An → integer N if there exists a → right triangle with → rational sides so that the area of the triangle is N. For example, the number N = 6, because of the 3-4-5 triangle.

congruent; → number.

conjugate complex number
  عدد ِ همتافت ِ همیوغ   
adad-e hamtâft hamyuq (#)

Fr.: nombre complexe conjugé   

The conjugate of a → complex number, expressed by ū = a - bi. The complex number and its conjugate have the same real part. Same as → complex conjugate.

conjugate; → complex; → number.

coordination number
  شمار ِ هم‌آرایش   
šomêr-e hamârâyeš

Fr.: nombre de coordination   

1) Crystallography: The number of nearest neighbors of an atom or ion in a → crystal lattice. A large coordination number indicates that the structure is more closely packed.
2) Chemistry: The number of atoms, ions, or molecules surrounding a central atom or ion in a complex.

coordination; → number.

data number (DN)
  شمار ِ داده‌ها   
šomâr-e dâdehâ


Unit of the analog-to-digital conversion system of a CCD apparatus. For example a 16 bit system may use a maximum of 65536 DN. The acronym ADU, for analog-to-digital unit, is also used.

data; → number.

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