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

He who, or that which, federates.

Agent noun of → federate + → -or.

1) To give food to; supply with nourishment.
2) To furnish with necessary material.

M.E. feden, from O.E. fedan "to nourish;" cf. O.S. fodjan, O.Fris. feda, Goth. fodjan "to feed."

Xorândan, transitive form of xordan "to eat, consume," Mid.Pers. xvardan "to eat, enjoy (food)," Av. x^var "to consume, eat;" Laki dialect hovârden "to eat;" Proto-Iranian *huar- "to consume, eat."

1) For any system that has an → input and → output, the return of a fraction of the output to the input for the next action. Feedback process allows a system to regulate itself by monitoring its own output. It is of prime importance to the working of all regulatory mechanisms found in living and non-living nature, as well as in social systems such as education and economy.
2) By extension, any response or information about the result of a process.
3) → stellar feedback.
See also: → feedback loop, → negative feedback, → positive feedback, → radiative feedback, → feedforward.

→ feed; → back.

A closed transmission path in a → feedback process involving part of the → output as an → input for correction or control of the operation of a → system.

→ feedback; → loop.

In a self-regulatory system, monitoring a disturbance before it enters the → system to apply corrections before the disturbance has influenced the system. See also → feedback.

→ feed; → forward.

In a → radio telescope, a device located at the → focal point of the → antenna. It receives the → radio waves which the antenna collects and guides them to the → detector.

→ feed; → horn.

1) To perceive or examine by touch.
2) To have a sensation of (something), other than by sight, hearing, taste, or smell (Dictionary.com).

M.E. felen, from O.E. felan "to touch;" cf. O.S. gifolian, O.Fr.fela, Du. voelen, O.H.G. vuolen, Ger. fühlen "to feel;" from PIE root *pal- "to touch, feel, shake, strike softly" (cognates: Gk. psallein "to pluck (the harp)," L. palpare "to touch softly, stroke").

Sohidan, from Mid.Pers. sôhistan "to feel, to touch," sôhešn "feeling, sense," of unknown origin. Note Pers. sahestan "to fear," from Proto-Ir. *θrah- "to shake; to fear;" Pers. tars, harâs, sham "fear;" may be they are of different roots.

1) The function or the power of perceiving by touch.
2) Physical sensation not connected with sight, hearing, taste, or smell.
3) A particular sensation of this kind (Dictionary.com).

Verbal noun of "to → feel."

A group of rock-forming minerals whose members are the most abundant constituents of igneous rocks. They consist of aluminum silicates of potassium, sodium, and calcium and typically occur as colorless or pale-colored crystals.

Modification of obsolete Ger. Feldspath (now Feldspat), from Ger. Feld "field" + obsolete Ger. Spath (now Spat) "spar."

1) Of, relating to, or being the sex that typically has the capacity to bear offsprings or produce eggs. 2) A female person, animal, or plant.

M.E., alteration of femel, femelle, from O.Fr. femelle "woman, female," from M.L. femella "a female," from L. femella "young female, girl," diminutive of femina "woman, a female," → feminine.

Mâdé "female," from Mid.Pers. mâdag, "female," from mâd, → mother.

1) Characteristic of or appropriate or unique to women.
2) Of, relating to, or constituting the gender that ordinarily includes most words or grammatical forms referring to females (Merriam-Webster.com).

M.E. feminin, from O.Fr. femenin "feminine, female; with feminine qualities," from L. femininus "feminine," from femina "woman, female," literally "she who suckles," from root of felare "to suck, suckle;" cf. Gk. thele "mother's breast, nipple," thelys "female, fruitful;" Pers. dâyé, dâyah "(wet-nurse);" PIE root *d^he(i)- "to suck, suckle."

Mâdin, from mâdé, → female.

1) Belief in the social, political, and economic freedom of women and equality of the sexes. Feminism is closely tied to democracy and → secularism.
2) The movement organized around this belief.

From Fr. féminisme, from féminin "feminine, female," from L. femininus "feminine" (originally in the grammatical sense), from femina "woman, female," literally "she who suckles," cognates fecund "fruitful, fertile," felix "happy," fetus "offspring, pregnancy;" PIE base *d^heh(i)- "to suck, suckle;" cf. Gk. thele "mother's breast;" Pers. dâyé "wet nurse."

Zâd-zan-bâvari, from zâdzan "free woman" (on the model of zâdmard "free man, valiant man, generous man," zâdsarv "tall and upright cypress tree"), from zâd, contraction of âzâd, → free, + zan, → woman, + bâvari, → -ism.

In the International System of Units, a prefix meaning 10^-15.

From Danish and Norwegian femten "fifteen," from O.N. fimmtān (Sw. femton, Du. vüftien, Ger. fünfzehn, E. fifteen, Pers. pânzdah), ultimately from PIE base *penk^we "five" (cf. Mod.Pers. panj, Av. panca, Skt. pánca, Gk. pente, L. quinque) + PIE *dekm "ten" (cf. Mod.Pers. dah, Av. dasa, Skt. dáśa, Arm. tasn, Gk. deka, L. decem, Ger. zehn, E. ten, Fr. dix).

Any number of the form 2²ⁿ + 1, where n is a connective → integer. If Fermat number is → prime, it is called a → Fermat prime.

→ Fermat's principle; → number.

A → Fermat number, 2²ⁿ + 1, that is a → prime number. The only known Fermat primes are: 3, 5, 17, 257, and 65537, corresponding to n = 0, 1, 2, 3, and 4.

→ Fermat's principle; → prime.

In → number theory, the statement that for all → integers, the equation xⁿ + yⁿ = zⁿ has no solution in → positive integer. After 358 years of effort by mathematicians to prove the theorem, a complete proof was found by Andrew Wiles in 1995.

→ Fermat's principle; → last; → theorem.

The path taken by a ray of light going from one point to another through any set of media is such that the time taken is a minimum. This principle governs the light propagation and determines the geodesics of optical paths.

Put forward by Pierre de Fermat (1601-1665), French mathematician, born at Beaumont-de-Lomagne; → principle

A unit of length equal to 10^-13 cm.

After Enrico Fermi (1901-1954), the Italian-born American physicist who was a key figure in the development of nuclear physics. He was awarded the 1938 Nobel Prize for Physics.

The → coupling constant associated with the → weak interaction, which gives rise to → beta decay. C_F = 1.167 x 10^-5 GeV^-2.

→ Fermi; → constant.

The energy of the highest occupied quantum state in a system of fermions at absolute zero temperature. See also → Fermi sea.

→ fermi; → energy.