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

1) The lowest or deepest part of anything, as distinguished from the → top. The under or lower side; underside. → bottom-up structure formation.
2) → bottom quark.

M.E. botme; O.E. botm, bodan "ground, soil, lowest part" (cf. O.Fris. boden "soil," O.N. botn, O.H.G. bodam, Ger. Boden "ground, earth, soil"), akin to Pers. bon "basis; root; foundation; bottom;" Mid.Pers. bun "root; foundation; beginning;" Av. būna- "base, depth" (Skt. bundha-, budhná- "base, bottom," Pali bunda- "root of tree;" Gk. pythmen "foundation;" L. fundus "bottom, piece of land, farm," O.Ir. bond "sole of the foot").

Tah "bottom; end" (Mid.Pers. tah "bottom." The origin of this term is not clear. It may be related to PIE *tenegos "water bottom;" cf. Gk. tenagos "bottom, swamp," Latvian tigas, from *tingas, from *tenegos "depth").
Pâyin "bottom, below; at the foot of," from pâ(y) "foot; step" (Mid.Pers. pâd, pây; Av. pad- "foot;" cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis (Fr. pied); P.Gmc. *fot (E. foot; Ger. Fuss); PIE *pod-/*ped-); + -in a relation suffix.

A → structure formation scenario in which small galaxies form first, and larger structures are then formed in due course. Contrary to → top-down structure formation.

→ bottom; → up; → structure; → formation; → galaxy.

1) (adj.) Tied, confined by bonds. → bound cluster, → bound charge, → bound system.
2) (n) a boundary; a limit.

1) p.p. of → bind. 2) → boundary.

Any electric charge which is bound to an atom or molecule, in contrast to free charge, such as metallic conduction electrons, which is not. Also known as → polarization charge.

→ bound; → charge.

A cluster of astronomical objects, such as stars or galaxies, held together by their mutual gravitational attraction. → bound system.

Bound, p.p. of → bind; → cluster.

Xušé, → cluster; bandidé p.p. of bandidan, → bind.

Any → occurrence of a → variable  x in an x-bound part of a → wff.

→ bound; → occurrence.

The orbit described by an object around a central gravitational force in a system whose total energy is negative. An elliptical orbit.

Bound, p.p. of → bind; → orbit.

Madâr, → orbit; bandidé, p.p. of bandidan, → bind.

A system composed of several material bodies the total energy of which (the sum of kinetic and potential energies) is negative, e.g. a → bound cluster.

Bound, p.p. of → bind; → system.

Aâžmân, → system; bandidé p.p. of bandidan, → bind.

A transition between two energy levels of an electron bound to a nucleus. The electron remains tied to the nucleus before and after the transition. → bound-free transition; → free-free emission.

Bound, p.p. of → bind; → transition.

A transition in which a bound electron is liberated. → free-bound emission; → free-free emission.

Bound, p.p. of → bind; → free.

1) General: Something that indicates a border or limit; the border or limit so indicated.
2) Thermodynamics: A conceptual closed surface useful in separating and distinguishing a system from its surroundings.
3) Math.: In topology, the boundary of a subset S of a topological space X is the set of points which can be approached both from S and from the outside of S.
4) Electronics: An area of meeting of P-type and N-type → semiconductor materials where the → donor and → acceptor concentrations are equal.

From Fr., from O.Fr. bodne, from M.L. bodina, butina "boundary, boundary marker."

Karân, karâné, kenâr from Mid.Pers. karânag, Av. karana- "boundary."

1) Math: Restriction on the limits of applicability of an equation. In a differential equation, conditions that allow to fix the constant of integration and reach a unique solution. The number of boundary conditions necessary to determine a solution matches the order of the equation.
2) Physics: Conditions needed to determine the evolution of a system, given the physical laws.

→ boundary; → condition.

An effect that forbids or invalidate locally the use of an idealized model of a system in which one or several of its dimensions are supposed to be infinite.

→ boundary; → effect.

A layer of fluid that is formed wherever a fluid flows past a solid surface and the effects of → viscosity are important. The boundary level forms because as the fluid moves past the object, the molecules which are in direct contact with the surface stick to the surface. The molecules just above the surface are slowed down in their collisions with the molecules sticking to the surface. These molecules in turn slow down the flow just above them, but less effectively. This creates a thin layer of fluid near the surface in which the velocity changes from zero at the surface to the free stream value away from the surface. The boundary layer may be either → laminar or → turbulent in character, depending on the value of the → Reynolds number. The concept of boundary level was first put forward by Ludwig Prandlt (1875-1953) in 1904.

→ boundary; → layer.

General: Having bounds or limits.
Math.: Of a function, having a range with an upper bound and a lower bound.

Adj. from → bound.

The function y = f(x) in a given range of the argument x if there exists a positive number M such that for all values of x in the range under consideration the inequality | f(x) | ≤ M will be fulfilled. → unbounded function.

→ bounded; → function.

A simplification in the equations of → hydrodynamics that treats the density as constant except in the → buoyancy term. This approximation is motivated by the fact that when pressure and temperature differences in a flow are small, then it follows from the thermodynamic → equation of state that a change in the density is also small.

Named after Joseph Valentin Boussinesq (1842-1929), a French physicist who made significant contributions to the theory of hydrodynamics, vibration, light, and heat; → approximation.

1a) A bent, curved, or arched object.
1b) A weapon made of a curved, flexible strip of material and a cord connecting the two ends that is used to launch an arrow. 2) The front of a ship or boat; prow; opposite to stern or poop, → Puppis.

1) M.E., from O.E. boga "archery bow, arch, rainbow" (cf. O.Norse bogi, Du. boog, Ger. Bogen "bow"); PIE root *bheug- "to bend;" cf. Skt. bhujati "bends;" O.H.G. boug, O.E. beag "a ring").
2) M.E. boue, from O.N. bogr or M.Du. boech "bow of a ship."

1) Kamân "bow, arc," from Mid.Pers. kamân, related to xam "curve," cf. Breton kamm "curved, bent," Gk. kampe "a corner, a joint," L. campus "a field," Lith. kampus "corner," PIE *kamb- "to bend, crook." Farâl, from farâ "forward" (farâ raftan "to go forward, proceed," farâ rândan "to drive forward"), equivalent to → pro-, + relation suffix -âl, → -al. Compare farâl with prow "bow," Fr. la proue "prow, bow," from dialectal It. proa, prua, from L. prora "bow," from Gk. proira, related to pro "before, forward."

A → shock wave created in front of an object moving through a medium with a velocity higher than that of the → sound waves in that medium. See, for example, → magnetosphere.

→ bow; → shock.

The wave which appears in front of a speeding boat and goes out behind it in a distinctive "V". It is due to the fact that waves pile up on each other before they can move away.

→ bow; → wave.