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

The → acceleration of a particle at time t defined by a = lim Δv/Δt = dv/dt. It is the limiting value of Δv/Δt at time t as both Δv and Δt approach zero.

→ instantaneous; → acceleration.

The act of instigating; incitement.

Verbal noun of → instigate.

The mathematical form of the way an instrument affects the input signal.

→ instrumental; → response; → function.

1) The design and use of scientific instruments for detection, measurement, control, computation, and so on.
2) The ensemble of instruments contained in a given machine or system.

From → instrument + -ation a combination of -ate and -ion, used to form verbal nouns.

Sâzâlgari, noun from sâzâlgar, → instrumentalist. Sâzâlgân, with plurality suffix -gân.

1) The act or fact of insulating.
2) Any material used to reduce or prevent the transfer of electricity, heat, cold, or sound.

Verbal noun from → insulate.

An expression of an integer nas the sum of one or more positive integers. The number of different partitions of n is denoted p(n). This function is called the partition function. For example, p(5) = 7, because 5 can be partitioned as: 5 = 5 = 4 + 1 = 3 + 2 = 3 + 1 + 1 = 2 + 2 + 1 = 2 + 1 + 1 + 1 = 1 + 1 + 1 + 1 + 1.

→ partition; → integer.

An equation involving an unknown function that appears as part of an integrand.

→ integral; → equation.

A function whose image is a subset of the integers, i.e. that takes only integer values.

→ integral; → function.

In calculus the operation which consists of finding the areas enclosed by curves through the summations of infinitesimals. The inverse process of differentiation.

Verbal noun of → integrate.

The time during which a detector integrates the incoming photons.

→ integration; → time.

The action of making or becoming stronger or more extreme.

verbal noun of → intensify.

The rate of emitted energy from unit surface area through unit solid angle. The radiation from a surface has different intensities in different directions.

→ intensity; → radiation.

General: Mutual or reciprocal action or influence.
Physics: 1) What happens between a system and its surroundings when an observable change in one corresponds to or correlates with an observable change in the other.
2) The natural phenomenon of the transfer of energy between two particles. The four known kinds of interactions, in the order of increasing strength, are: → gravitational, → weak, → electromagnetic, and → strong.

Interaction, from → inter-; + → action.

Capable of acting on or influencing each other

From → interaction; + → -al.

A low-density region separating the spiral arms of a galaxy.

Interarm, from → inter- + arm "body part," from O.E. earm "arm," from P.Gmc. *armaz (cf. M.Du., Ger. arm, O.N. armr, O.Fris. erm), from PIE base *ar- "to fit, join;" Mod.Pers. arm "arm, from the elbow to the shoulder;" Av. arma-, arəmo- "arm;" Skt. irma- "arm;" Gk. arthron "a joint," L. armus "shoulder;" → region.

Andarbâzu, from andar-, → inter-, + bâzu "arm," from Mid.Pers. bâzûk "arm;" Av. bāzu- "arm;" cf. Skt. bāhu- "arm, forearm;" Gk. pechys "forearm, arm, ell;" O.H.G. buog "shoulder;" Ger. Bug "shoulder;" Du. boeg; O.E. bôg, bôh "shoulder, bough;" E. bough " a branch of a tree;" PIE *bhaghu- "arm"); nahiyé, → region. Andararm, from andar-, → inter-, + arm, as above.

The act of intercalating; insertion. Something that is intercalated.
Astro.: An insertion into a calendar, → intercalate.
Geology: The presence of a body of rock interbedded with another body of different rock.

The verbal noun of → intercalate.

Reciprocal connection between two or several things.

→ andar-; → connection.

In spectroscopy, same as → semi-forbidden line.

→ interconnection; → line.

→ Absorption features in the spectra of bright sources like → quasars attributed to a tenuous matter filling the medium between galaxies.

→ intergalactic; → absorption.

Of an → H II region, the absorption of photons by the dust which is mixed with ionized gas, in contrast to the absorption by the → interstellar dust on the line of sight.

→ internal; → absorption.