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

A parameter, denoted k = 2π/λ, that along with the → angular frequency, ω = 2πν, is used to express the equation of → simple harmonic motion, y = cos (ωt - kx + π/2). Same as → wave number.

→ propagation; → number.

To drive, or cause to move, forward or onward.

From L. propellere "to push forward," from → pro- "forward" + pellere "to push, drive."

Pišrândan, from piš "before; in front," from Mid.Pers. pêš "before, earlier," O.Pers. paišiya "before; in the presence of" + rândan "to push, drive, cause to go," causative of raftan "to go, walk, proceed" (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").

A propelling agent. A substance, usually a mixture of fuel and oxidizer, for propelling a rocket.

From → propel + suffix -ant.

Pišrâné, from pišrândan, → propel.

Belonging or pertaining exclusively or distinctly to a person, thing, or group. → proper mass; → proper motion; → proper time.

M.E., from O.Fr. propre, from L. proprius "one's own."

Saré "pure; principal."

A distance between two nearby events in the frame in which they occur at the same time. It is the distance measured by a ruler at the time of observation. Hence, for a cosmological time t, D_proper = D_C . a(t), where D_C is the → comoving distance, and a(t) is the → scale factor. In the present epoch a = a(t_obs) = 1, and D_proper = D_C.

→ proper; → distance.

Same as → rest mass.

→ proper; → mass.

The apparent motion of a star across the sky (not including a star's parallax), arising from the star's velocity through space with respect to the Sun. Proper motion is usually tabulated in star catalogs as changes in right ascension and declination per year or century. See also: → proper motion distance.

→ proper; → motion.

The distance derived from the → proper motion of an object. If an object has a known → transverse velocity  u, and has an observed angular motion of dθ/dt, then the proper motion distance is defined as: d = u/(dθ/dt).

→ proper; → motion; → distance

Of two sets A and B, the set A if it is contained in B (A ⊂ B) but is not equal to B (A ≠ B).

→ proper; → subset.

In general relativity, the time as measured on a clock that travels with the observer in the same system. An accelerated clock will measure shorter time intervals between events than a non-accelerated clock between the same events. → twin paradox.

→ proper; → time.

1) General: An essential or distinctive attribute or quality of a thing.
2) Physics: A quantity, such as length, mass, pressure, temperature, or volume, that relates to the state of a system and can be expressed in numbers obtained from well-defined measurement operations.

From M.E. propriete "ownership, something owned, one's own nature," from M.Fr. propriété, from L. proprietas "ownership, property, propriety," literally "special character," noun of quality from proprius "one's own, special."

Dârâk "thing owned," from dâr present stem of dâštan "to have, to possess" + -âk (on the model of xorâk, pušâk, kâvâk). The first element dâštan, from Mid.Pers. dâštan, O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" Skt. dhr- "to to hold, keep, preserve," dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *d^her- "to hold, support."

A circumstellar disk of dense gas and dust surrounding a young newly formed star, a T Tauri star or Herbig star. In particular, an externally ionized protoplanetary disk seen in emission in the Orion Nebula. → silhouette disk.

Contraction of protoplanetarydisk.

Comparative relation between things, sizes, quantities, numbers, parts, etc.
Math.: A statement of the equality of two ratios.

M.E. proporcio(u)n, from O.Fr. proportion, from L. proportio "comparative relation, analogy," from the phrase pro portione "according to the relation" (of parts to each other), from pro "for" + portio "part, shar."

Barpâreš, from bar- "on; up; upon; in; into; at; forth; with; near; before; according to" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + pâr "part, portion, piece" (variants pâréparré "portion, segment (of an orange)," pargâlé, "piece, portion; patch;" (dialects Kermâni pariké "portion, half;" Tabari perik "minute quantity, particle;" Lârestâni pakva "patch;" Borujerdi parru "patch"); Mid.Pers. pârag "piece, part, portion; gift, offering, bribe;" Av. pāra- "debt," from par- "to remunerate, equalize; to condemn;" PIE *per- "to sell, hand over, distribute; to assigne;" Gk. peprotai "it has been granted;" L. pars, as above; Skt. purti- "reward;" Hitt. pars-, parsiya- "to break, crumble") + -eš suffix.

Being in or characterized by proportion.
Math.: Of two quantities, having the same or a constant ratio or relation.

→ proportion + → -al.

A device in which an electronic detection system receives pulses that are proportional to the number of ions formed in a gas-filled tube by ionizing radiation.

→ proportional; → counter.

Math.: A relationship bewteen two quantities such that if one quantity changes the other changes in the same proportion; denoted as y ∝ x.

→ proportional + → -ity.

Math.: A → constant that converts a proportionality into an → equation. Thus the proportionality constant k converts the proportionality y ∝ x into the equation y = kx.

→ proportionality + → constant.

To offer or suggest (a matter, subject, case, etc.) for consideration, acceptance, or action (Dictionary.com).

M.E., from M.Fr. poposer, from → pro- "forth," + poser "put, place," → position.

Farâhelidan, from farâ-, → pro-, + helidan, heštan "to place, put" from Mid.Pers. hištan, hilidan "to let, set, leave, abandon," Parthian Mid.Pers. hyrz; O.Pers. hard- "to send forth," ava.hard- "to abandon;" Av. harəz- "to discharge, send out; to filter;" hərəzaiti "releases, shoots;" cf. Skt. srj- "to let go or fly, throw, cast, emit, put forth;" Pali sajati "to let loose, send forth."

1) The act of offering or suggesting something to be considered, accepted, adopted, or done.
2) A plan or scheme proposed.
3) Logic: A statement in which something is affirmed or denied, so that it can therefore be significantly characterized as either true or false.
4) Math.: A formal statement of either a truth to be demonstrated or an operation to be performed; a theorem or a problem (Dictionary.com).

Verbal noun of → propose.

Logic: Of, relating to, or in the form of a → proposition.

→ proposition; → -al.