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

Of or pertaing to → precession.

→ precession; → -al.

The path of either → celestial poles around the → ecliptic pole due to the → precession of equinox. It takes about 26,000 years for the celestial pole to complete path.

→ precessional; → circle.

1) Meteo.: Any form of water, such as rain, snow, sleet, or hail, that falls to the Earth's surface. The quantity of such water falling in a specific area within a specific period.
2) Chemistry: The process of separating a solid substance from a solution.

From M.Fr. précipitation, from L. præcipitationem "act or fact of falling headlong, haste," from præcipitare "fall, be hasty," from præceps "steep, headlong, headfirst," from præ- "forth" + caput, → head.

1) Bâreš, verbal noun of bâridan "to rain," bârân "rain;" Mid.Pers. vâritan, vârân; Av. vār- "rain; to rain;" cf. Skt. vār- "rain, water; to rain;" PIE base *uer- "water, rain, river."
Rizeš, verbal noun of rixtan "to flow, to pour," → overflow.
2) Tahnešast "to settle down, precipitate," from tah "→ bottom, end;" + nešast past stem of nešastan "to sit down; to settle down; to sink," → sit.

1) The state or quality of being → precise.
2) The degree to which repeated measurements of a quantity give the same results under unchanged conditions. Not the same as → accuracy, but often confused as such. See → accuracy for the difference between precision and accuracy.

Verbal noun from → precise.

1) Act of plundering or robbing; predatory behavior.
2) The preying of one animal on others.

Verbal noun, → prey.

1) Zoology Psychology: The action of grasping or seizing.
2) Philosophy: An interaction of a subject with an event or entity which involves perception but not necessarily cognition (Oxford Dictionary, lexico.com).

Verbal noun of → prehend.

In → particle physics, any of postulated "point-like" particles from which are composed → quarks and → leptons. In other words, preon models assume there is a more fundamental kind of particle than those so far known. Different preon models consider different numbers and different natures of the preons.

Coined by Jogesh Pati and Abdus Salam in 1974, from → pre- + → -on.

A word used with a noun or pronoun to mark its relation with another word.

From L. praepositionem "a putting before," from praepositus, p.p. of praeponere "put before," from prae "before," → pre-, + ponere "put, set, place," → position.

Pišhel, from piš-, "before," → pre-, + hel-, helidan, heštan "to place, put," → leap.

1) An act of prescribing.
2) A direction, usually written, by the physician to the pharmacist for the preparation and use of a medicine or remedy. The medicine prescribed (Dictionary.com).

Verbal noun of → prescribe; → -tion.

The present number of stars on the → main sequence per unit logarithmic mass interval per square parsec. The PDMF is the basis for deriving the → initial mass function (IMF). This mass function is not corrected for stellar evolution nor losses through stellar deaths.

→ present; → day; → mass; → function.

A physical state of dense matter in which the electrostatic field of one atom should influence a neighboring atom and hence disturb atomic levels. In extreme case, such as white dwarfs, electron clouds practically rub and electrons are ionized off the parent atoms.

→ pressure; → ionization.

In cosmological models, the phenomenon that is supposed to seed the → cosmic microwave background anisotropies and the structure formation of the Universe.

→ primordial; → curvature; → perturbation.

Newton's third law of motion, which states that for every action there must be an equal and opposite reaction.

→ principle; → action; → reaction.

The second postulate in Einstein's theory of → special relativity whereby the → velocity of light in → vacuum has the same absolute value in all → inertial reference frames irrespective of the direction and speed of propagation of the light source. It should be emphasized that this constancy of the speed of light holds among → reference frames moving uniformly with respect to each other. An observer accelerated with respect to a light source will measure a speed of light that is smaller than the speed of light measured in a → rest frame. See also → principle of relativity.

→ principle; constancy, noun related to → constant.

The principle that, for a system whose total mechanical energy is conserved, the path to be taken for the system from one configuration to another is the one whose action has the least value relative to all other possible paths and from the same configurations. Also called Maupertuis' principle, least-action principle.

→ principle; → least; → action.

The third principle of → formal logic introduced in Aristotle's theory of the → syllogism: No statement can be both → true and → false at the same time. Also called → law of non-contradiction.

→ principle; → non-; → contradiction.

A font used for printing. See also → screen font.

→ printer; → font.

The transfer from public to private ownership.

→ private; → -tion.

A mathematical function whose integral over any interval gives the probability that a continuous → random variable has values in this interval. Also known as → density function, frequency function, → probability function.

→ probability; → density; → function.

The function that describes the range of possible values that a random variable can attain and the probability that the value of the random variable is within any (measurable) subset of that range.

→ probability; → distribution.