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

1) General: Having actual physical existence; genuine, not artificial.
2) Math.: Involving, relating to, or having elements of the set of rational or irrational numbers only.
3) Philo.: Existent or pertaining to the existent as opposed to the nonexistent; actual as opposed to possible or potential.
See also:
→ real dynamical variable, → real equator, → real equinox, → real fluid, → real gas, → real image, → real number, → real object, → real-time operation, → real-time processing, → realism, → realist, → realistic, → reality, → true.

M.E., from O.Fr. reel, from L.L. realis "relating to things; actual," from L. res "matter, thing," of unknown origin.

Hasyâ, from O.Pers. hašya- "true, real;" Av. haiθa- "true, real;" cf. Khotanese hiththo "true, real;" Ossetic aecaeg "true, real, genuine;" Skt. satyá- "true, real, genuine;" PIE base *es- "to be" (Mod.Pers. hastan, astan "to be;" O.Pers./Av. ah-, Skt. as-).

A → dynamical variable which does not have an → imaginary number part.

→ real; → dynamical; → variable.

Same as → true celestial equator.

→ real; → equator.

Same as → true equinox.

→ real; → equinox.

The opposite of an ideal fluid; a fluid which possesses viscosity and therefore exhibits certain frictional phenomena. Viscosity arises due to cohesive forces between molecules and molecular momentum exchange between fluid layers. These effects appear as tangential or shear stresses between moving fluid layers.

→ real; → fluid.

Actual gas whose molecules do not necessarily possess the properties assigned to those of an → ideal gas.

→ real; → gas.

In an optical system, the image of an object produced by the convergence of the light rays that make up the image. → virtual image; → real object.

→ real; → image.

A number that can be represented by a point on a line. The set of real numbers includes all rational and irrational numbers, but not the imaginary numbers.

→ real; → number.

In an optical system, a collection of points which actually serves as a source of light rays.

→ real; → object.

The operation of a computer during the actual time that the related physical processes take place so that the results can be used to guide the physical processes.

→ real; → time; → operation.

Data processing that takes place instantaneously upon data entry or receipt of a command.

→ real; → time; → processing.

1) An inclination or concern for the actual or real, as distinguished from the abstract or speculative.
2) Philo.: The doctrine that material objects exist independently of our perception of them.
3) Art, literature: The attempt to describe the objects or social conditions as they actually are, without idealization or presentation in abstract form.

→ real; → -ism.

1) A person who tends to view or represent things as they really are; an adherent of → realism.
2) Of or pertaining to realism or to a person who embodies its principles or practices.

→ real; → -ist.

1) Interested in, concerned with, or based on what is real or practical.
2) Philo.: Of or pertaining to realists or → realism.

From → real + -istic, from L. -isticus, Gk. -istikos, from -ikos, → -ic.

1) The state or quality of being real. A real thing or fact.
2) Philo.: The totality of what is, as opposed to what merely seems to be.

→ real + → -ity.

In reality; actually; indeed.

→ real; → -ly.

1) A basis or cause, as for some belief, action, fact, event, etc.
2) A statement presented in justification or explanation of a belief or action.
3) The mental powers concerned with forming conclusions, judgments, or → inferences especially in orderly rational ways.
Philo.: The intellectual ability to apprehend the truth cognitively, either immediately in intuition, or by means of a process of inference. See also → wisdom.
4) (v.) To think or argue in a logical manner; to form conclusions, judgments, or inferences from facts or premises.

M.E. resoun, reisun (n.), from O.Fr. reisun, reson, raison, from L. rationem (nom. ratio) "reckoning, understanding, motive, cause," from ratus, p.p. of reor, reri "to reckon, think;" cognate with Pers. râ, rây "reason," as below; O.C.S. raditi "to take thought, attend to," O.Ir. im-radim "to deliberate, consider."

Râyan, from rây + -an. The first component rây, râ "because of, by reason of," in barây-e "because of," cerâ "for what reason, why?," irâ "for this reason, therefore," zirâ "because, on account of;" also rây "opinion, consult;" râymand "reasonable, wise;" râyzan "a person whom one consults; wise;" Mid.Pers. râd, rây "because of, for the sake of, on behalf of;" O.Pers. rā "reason, cause," in rādiy "for this reason;" Av. rādah- "generosity, care, generous," rāsta- "to do right, to fit;" cf. Skt. rādh- "to succeed, be successful;" Gk. arithmos "number, amount;" L. ratio, as above; PIE base *rē-, *rə-. The second component -an a suffix as in rowzan, rowšan, suzan, rasan, zaqan, hâvan, etc.

Being in accordance with reason.

→ reason; → -able.

A process of thinking involving → inference, or of solving problems by employing general principles.

Verbal noun of → reason.

A temperature scale in which the → freezing point and the → boiling point of → water are set to 0 and 80 degrees respectively. See also → Celsius scale, → Fahrenheit scale, → Kelvin scale, → Rankine scale.

Named after René Antoine Ferchault de Réaumur (1683-1757), who first proposed it in 1730; → scale.