An Etymological Dictionary of Astronomy and Astrophysics
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1) The degree of visibility of relevant → information in an image.
2) The → full-width at half-maximum of a long exposure stellar image obtained by an instrument mounted on a telescope observing in the presence of → seeing.

→ image; → quality.

A substance that is incorporated into a semiconductor material to provide free electrons (n-type impurity) or holes (p-type impurity).

Impurity, from im- negation prefix, → in-, + purity, O.Fr. pureté, from L.L. puritatem (nom. puritas) "cleanness, pureness," from purus "clean;" cf. Av. pūitika- "serving for purification," Mod.Pers. pâk "clean;" Skt. pavi- "to become clean," pávate "purifies, cleanses;" O.H.G. fouwen, fewen "to sift;" PIE base *peu- "to purify, cleanse."

Nâžâvi "impurity," from nâ- negation prefix, → in-, + žâv "pure" + -i noun suffix.

1) The condition of two things being so different in nature as to be unable to exist together.
2) Logic: (Of two or more propositions) unable to be true simultaneously.

→ incompatible; → -ity.

The particular character, or aggregate of qualities, that distinguishes one person or thing from others (Dictionary.com).

→ individual; → -ity.

1) A statement of the form a ≠ b, a > b, or a < b, asserting one quantity is greater than or less than another quantity. → equality.
2) An irregularity in the movement of a celestial object in its orbit about another which cannot be explained by their mutual gravitational attraction. Irregularities are often due to perturbation by other neighboring objects.

→ in-; → equality.

That quantity which is greater than any assignable quantity.

Noun form of → infinite.

The condition or an instance of not being homogeneous.

→ in- "not" + → homogeneity.

An instant of infinite density, infinite pressure, and infinite temperature where the equations of general relativity break down, if the standard Big Bang theory is extrapolated all the way back to time zero. → singularity.

→ initial; → singularity.

The quality or state of being insecure; something insecure.

→ in-; → security.

The condition of a system when it is disturbed by internal or external forces. The system continues to depart from the original condition, in contrast to a stable system, which will return to its previous condition when disturbed.

From → in- "not" + → stability

A narrow, almost vertical, band on the right hand side of the → main sequence in the → H-R diagram occupied by many different types of → pulsating stars (→ RR Lyrae, → Cepheids, → W Virginis, → ZZ Ceti). Stars traverse this region at least once after they leave the main sequence. The narrow temperature range of the instability strip corresponds to the stellar → effective temperature that can sustain → partial ionization zones, capable of maintaining stellar oscillations. The blue (hot) edge of the instability strip pertains to stars with surface temperatures hotter than ~ 7500 K. Because these stars have partial ionization zones too close to their surface, the pulsation mechanism is not active. The red (cooler) edge of the instability strip is determined by stars with a temperature lower than ~ 5500 K. In these stars convection prevents the build-up of heat pressure necessary to drive pulsations.

→ instability; → strip.

The velocity of a particle at some one instant of time, or at some one point of its path. It can be defined as the limiting value of the average velocity when the second point is taken closer and closer to the first point.

→ instantaneous; → velocity.

General: The quality or condition of being intense.
Physics: Strength, as of energy or a force per unit of area, solid angle, time, etc.; e.g. → electric intensity; → magnetic intensity.

From → intense + → -ity.

Dartanuyi state, condition noun of dartanu, → intense.

The height of a spectral line above the continuum base.

→ intensity; → line.

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.

A wave generated inside a density-stratified fluid under the influence of → buoyancy forces. Known also as → gravity wave or internal wave.

→ internal; → gravity; → wave.

The ability of different types of computers, networks, operating systems, and software applications to work together by exchanging and sharing information in a standardized, accurate, and effective manner.

→ inter-; → operability.

The energy per second emitted by an astronomical object.

→ intrinsic; → luminosity.

Lack of → validity.

→ invalid; → -ity.

A bump appearing in the plot of stellar → opacity versus temperature. The ionization of the heaviest → chemical elements, especially → iron, which is the most abundant heavy metal, produces a large number of weak spectral → absorption lines. These lines dominate the stellar opacity in the temperature range 10⁵-10⁶ K and furnish two local opacity peaks: a large peak around 2 × 10⁵ K and a smaller one around 1.5 × 10⁶ K (Rogers & Iglesias, 1992, ApJS 79, 507; Iglesias et al. 1992, ApJ, 397, 717).

→ iron; → opacity; → peak.