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

The → plus sign +. It is believed to be a shortened form of the letters e and t in the L. word et, which, in early German manuscripts was the term for addition. The signs + and - were first used by Johann Wiedmann in 1489.

→ addition; → sign.

1) Involving → addition.
2) Something added to a substance to alter or improve it.

From L. additivus "added, annexed," from p.p. stem of addere, → add; → -ive.

1) Related to bardâyeš, → addition; 2) from bardây- prsent stem of bardâyidan, → add, + -é nuance suffix.

Color created by mixing light rays of different colors. Combining all the color rays of light results in white light. See also → subtractive color.

→ additive; → color.

The number which can be added to any other number without changing the magnitude of that number: zero. → multiplicative identity.

→ additive; → identity.

If E₁, E₂, ..., E_n are n → mutually exclusive events, then the probability of occurrence of at least one of them is the sum of their individual probabilities: P(E₁ + E₂ + ... + E_n) = P(E₁) + P(E₂) + ... + P(E_n).

→ additive; → law; → probability.

A binary star, in the constellation → Canis Major, 470 → light-years distant from Earth. The main star possesses an apparent magnitude of +1.5 and belongs to the spectral classification B2 II. The +7.5 magnitude companion star is 7''.5 apart from the main star.

Adhara, from Ar. adhârâ "virgins," plural of adhrâ' "virgin".

Azârâ, from Ar. Adhara.

1) To stay attached; stick fast; cling.
2) Physics: (of two or more dissimilar substances) to be united by a molecular force acting in the area of contact (→ adhesion).

From M.Fr. adhérer or directly from L. adhaerere "to stick to," from → ad- + haerere "to stick."

Âdusidan, from intensive/nuance prefix â- + dusidan (Dehxodâ) "to stick, to adhere," maybe related to Proto-Ir. *dauc- "to sew;" Pers. duxtan, duz- "to sew."

1) The act or state of adhering; adhesion.
2) The quality of adhering; steady devotion, support, or attachment (Dictionary.com).

→ adhere + -ence, → -ance.

1) A person who follows or upholds a leader, cause, etc.; supporter; follower.
2) Sticking; clinging; adhering (Dictionary.com).

From O.Fr. adherent or directly from L. adhaerentem pr.p. of adhaerere "to stick to," → adhere.

Âdusandé, from âdusidan, → adhere.

1) The act or state of adhering; state of being adhered or united.
2) Steady or devoted attachment, support, etc.; adherence.
3) Physics: The molecular force of attraction in the area of contact between unlike bodies that acts to hold them together (Dictionary.com). See also → cohesion.

Verbal noun from → adhere; → -tion.

1) Of or pertaining to the molecular force → adhesion.
2) A substance used for sticking objects or materials together; glue.

Adjective from → adhere.

The force of → attraction between molecules of different substances; for example, the force between the molecules of a solid and a liquid. When water is poured on clean glass, it tends to spread, forming a thin, uniform film over the surface. This is because the adhesive forces between water and glass are strong enough to pull the water molecules out of their spherical formation and hold them against the surface of the glass, thus avoiding the repulsion between like molecules.

→ adhesive; → force.

A → late-type → giant star of → spectral type K0-IIIb in → Andromeda. Other designations: ξ (Xi) Andromedae, HR 390, and HD 8207. → Visual magnitude = 4.88, B - V = +1.08.

From Ar. Al-dhayl "skirt of a garment; tail."

A → thermodynamic process that occurs without → loss or → gain of → heat.
See also: → adiabatic change, → adiabatic index, → adiabatic initial conditions, → adiabatic phase, → adiabatic process, → adiabatic shock, → adiabatic temperature gradient, → superadiabatic temperature gradient.

From Gk. adiabatos "impassable," from a- "not" + diabatos "passable," from diabainein "to go across," from dia- " through" + bainein "to go."

Bidarrow from bi- "not; without" + darrow "way out," from dar "out" + row "to go, going," from raftan "to go."

A change taking place in a system that has perfect thermal insulation, so that heat cannot enter or leave the system and energy can only be transferred by work.

→ adiabatic; → change.

Of a gas, the ratio of its → specific heat at constant pressure to its specific heat at constant volume: γ = C_P/ C_V.

→ adiabatic; → index.

The assumption whereby the density fluctuations in the very → early Universe would be produced by compressing or decompressing of all components of a homogeneous Universe. The adiabatic initial conditions lead to coherent oscillations in the form of peaks in the → temperature anisotropy spectrum. See also → acoustic peak, → baryon acoustic oscillation.

→ adiabatic; → initial; → condition.

Same as the → Sedov-Taylor phase.

→ adiabatic; → phase.

A → thermodynamic process in which no → heat is supplied to or rejected from a system. → polytropic process.

→ adiabatic, → process.

A → shock wave without → radiative cooling. The term "adiabatic" refers to the fact that no → heat is removed during shock.

→ adiabatic; → shock.