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

A prefix in the SI system of units denoting 10¹⁸.

Adopted in 1991, from Gk. ex "six," because it is equal to (1000)⁶.

1) Strictly accurate or correct; precise, as opposed to approximate.
2) The complete solution of an equation. For example, in the equation x² = 7, the positive solution 2.646 is correct to three decimal places. The exact answer is x = 7^1/2.
See also:
→ exact differential, → exact differential equation, → exact science, → accurate, → precise, → rigorous.

From L. exactus, p.p. of exigere, literally "to drive out, thrust out," also "demand, finish, measure," from → ex- "out" + agere "drive, lead, act," → act.

Razin "firm, solid, strong" [Dehxodâ, Steingass], Mid.Pers. razên "firm, strong, secure, solid."

If N(x,y) is a → function of two → independent variables, then dN = (∂N/∂x)dx + (∂N/∂y)dy is the exact differential.

→ exact; → differential.

A → differential equation composed of → continuous  → differentiable functions for which certain conditions are fulfilled. The equation M(x,y)dx + N(x,y)dy = 0 is called exact if M(x,y) and N(x,y) are continuous differentiable functions for which the following relationship is fulfilled: ∂M/∂y = ∂N/∂x, and ∂M/∂y and ∂N/∂x are continuous in some region.

→ exact; → differential; → equation.

A value that is known with complete certainty. Examples of exact numbers are defined numbers, results of counts, certain unit conversions. Some examples: there are exactly 100 centimeters in 1 meter, a full circle is exactly 360°, and the number of students in a class can exactly be 25.

→ exact; → number.

A field of study that admits especially precise predictions and rigorous methods of testing hypotheses, especially reproducible experiments involving quantifiable predictions and measurements.

→ exact; → science.

1) The act of examining; inspection; inquiry; investigation.
2) The state of being examined.
3) The act or process of testing pupils, candidates, etc., as by questions (Dictionary.com).

Noun from → examine.

1) To inspect or scrutinize carefully.
2) To inquire into or investigate.
3) To test the knowledge, reactions, or qualifications of (a pupil, candidate, etc.), as by questions or assigning tasks (Dictionary.com).

M.E., from M.Fr. examiner "interrogate, question," from L. examinare "to test or try; consider," literally "to weigh," from examen "a means of weighing or testing," probably ultimately from exigere "weigh accurately," → exact.

Barrasidan, from bar- "up; upon; on; in; into; at; forth; with; near; before; according to," → on-, + rasidan "to attain; to arrive," → access.

One of a number of things, or a part of something, taken to show the character of the whole.

From O.Fr. essample, from L. exemplum "a sample," literally "that which is taken out," from eximere "to take out, remove," from → ex- + emere "to obtain, buy," originally "to take," from PIE base *em- "to take" (cf. Av. yam-, yās- "to hold, take hold of," apayeiti (with apa) "taking away a thing from;" O.Pers. āyasa- "to take as one's own;" Skt. yam- "to hold, sustain," yamati "holds, subdues;" O.C.S. imo "to take;" Lith. imti, ima, émé "to take").

Nemuné, from nemun "index; guide," from nemudan "to show, display," from Mid.Pers. nimūdan, from ne- "down; into;" O.Pers./Av. ni- "down; below; into," → ni-, + mun, Av. māy- "to measure," → display.

Possessing outstanding quality or superior merit; remarkably good (Dictionary.com).

M.E., from O.Fr. excellent "outstanding," from L. excellentem (nominative excellens) "towering, prominent, superior," pr.p. of excellere "to surpass, be superior,"from → ex- "out from" + cellere "to rise high, tower," related to celsus "high, great," from PIE root *kel- "to be elevated; hill;" from which are derived L. collis "hill," columna "projecting object," culmen "top, summit," cellere "raise;" Gk. kolonos "hill," kolophon "summit;" Lithuanian kalnas "mountain," kalnelis "hill;" E. hill; Pers. dialects (Gilân) kol, kulâ "hill," (Dâmqân) kalut, kolut "successive soil hills, hill," (Tabari) keti "hill," (Jâsk) kit "hill."

Mid.Pers. pahrom "excellent," variant pahlom, ultimately from *parθama- "the highest, the most elevated," literally "Parthian," adj. from Parθa(va)-; cf. pahlavân "hero," another similar respect word related to Parthia (Nyberg 1974).

The center of an → excircle.

→ ex-; → center.

1) With the exclusion of; excluding.
2) To exclude; leave out.

From M.Fr. excepter , from L. exceptus, p.p. of excipere  "to take out," from → ex- "out" + capere "to take," → concept.

Sogert, from so-, variants zo- and os-, → ex- "out," + gert- "to take," → concept; cf. Mid.Pers. Parthian zgirw- "to take out," from uz- "ex-" + girw- "to take."

1) The act of excepting or the fact of being excepted.
2) Something excepted. 

Verbal noun of → except.

Forming an exception; not ordinary.

→ exception; → -al.

The state or an instance of surpassing usual, proper, or specified limits. → color excess; → infrared excess.

From L. excessus "going beyond bounds," from stem of excedere "to go beyond," from → ex- "out" + cedere "to go, yield;" cf. Gk. hodos "way;" PIE base *ked- "to go, yield."

Fozuni, from afzuni "excess," afzuni kardan "to exceed bounds," from afzudan "to add, increase," from Mid.Pers. abzudan "to increase, grow;" O.Pers. abijav- "to increase, add to, promote," from abi-, aiby- "in addition to; to; against" + root jav- "press forward;" Av. gav- "to hasten, drive;" Sk. jav- "to press forward, impel quickly, excite," javate "hastens."
Ferehbud "excess" (Mid.Pers. frehbūd "excess"), from Mod.Pers. fereh, firih "much; more" + bud "to be." The first component fereh, from Mid.Pers. frây "more, much," from Av. frāyah- "more; too much, very much" (frāyô.humata- "rich in good thoughts"). The second component bud, budan "to be," from Mid.Pers. budan, from O.Pers./Av. bav- "to be; become, take place;" Av. buta- perf. ptcpl. pass., bavaiti "becomes" (cf. Skt. bhavati "becomes, happens," bhavah "becoming; condition, state;" PIE *bheu- "to be, come into being, become;" Gk. phu- "become," phuein "to bring forth, make grow;" L. fui "I was" (perf. tense of esse), futurus "that is to be, future;" Ger. present first and second person sing. bin, bist; E. to be; O.Ir. bi'u "I am;" Lith. bu'ti "to be;" Rus. byt' "to be").

1) To give and receive reciprocally.
2) The act, process, or an instance of exchanging. → exchange force, → exchange particle, → Prevost's law of exchanges.

O.Fr. eschangier, from V.L. *excambiare, from L. → ex- "out" + cambire "barter."

Mod.Pers. gahulidan "to exchange," Kurd. guhartin/guhêr- "to exchange," Mid.Pers. wihir "to change," wihirišn "change," Manichean Mid.Pers. hr'g; Buddhist Mid.Pers. hlg "duty, tribute; work, effort;" Arm. loanword hark "duty, tribute;" Ar. loanword xarj "expense," xarâj "land, property tax;" Proto-Iranian *har- "to barter, trade; to pay tribute;" IE cognates: Gk. elein "to take (by force)," elor "loot, booty, catch;" Goth. saljan "to bring, to sacrifice;" O.E. sellan "to hand over, sell;" O.H.G. sala "delivery of goods."

The force that governs the exchange of particles in the interaction between bodies. → exchange particle.

→ exchange, → force.

In quantum field theory, a particle that transfers momentum and energy between interacting objects, and is said to mediate the interaction. All four of the fundamental forces involve the exchange of one or more particles. For example, photon is the exchange particle of the electromagnetic force.

→ exchange, → particle.

Chemistry: A complex formed from combination of a molecule with another molecule of the same type but in an → excited state. In other words, a → dimer in an electronically excited state. See also → exciplex.

From exci-, from → excited, + -mer, from → dimer.

Chemistry: A complex formed by association of a molecule in an → excited state and another molecule of a different type. See also → excimer.

From exci-, from → excited, + -plex, from → complex.