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

Occurring in nature; not artificially prepared. → nature.

Adj. of → nature.

Any frequency of small-amplitude oscillation for a system with a position of stable equilibrium and in the absence of external forces. In other words, the frequency of → free oscillation. Also called characteristic frequency.

→ natural; → frequency.

The → sciences, as → botany, → mineralogy, or → zoology, dealing with the study of all objects in → nature: used especially in reference to the beginnings of these sciences in former times (Dictionary.com).

→ natural; → history.

Linguistics: A language that has evolved naturally as a means of communication among people, as opposed to → artificial language and → formal language (Dictionary.com).

→ natural; → language.

The broadening of any spectral line due to the fact that excited levels have mean lives, which, by virtue of the uncertainty principle, implies a spread in the energy values.

→ natural; → line; → broadening.

The logarithm in which the → base is the → irrational number e = 2.718281828.... Also called → Napierian logarithm. The natural logarithm is denoted ln, an abbreviation of logarithmus naturalis. Natural logarithms are related to → common logarithms through: ln x = (1/M) log x, with M = (1/ln 10) ≅ 0.434294.

→ natural; → logarithm.

Either a member of the set of positive integers 1, 2, 3, ..., or the set of non-negative integers 0, 1, 2, 3, ... There seems to be no general agreement about whether to include 0 in the set of natural numbers.

→ natural; → number.

Of a body or system, the period of → free oscillation.

→ natural; → period.

A resonance such that the period of the driving force is the same as the natural period of the system.

→ natural; → resonance.

A solar system → object that → revolves around a → primary body and is not man made.

→ natural; → satellite.

A science that deals with matter, energy, their interrelations and transformations, In other words, natural sciences are concerned with physical processes observable in nature. They can be divided into physical and biological sciences.

→ natural; → science.

Physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants (e.g. the speed of light, Planck's constant, Boltzmann's constant, etc.) are equal to unity. The use of natural units allows these constants to be omitted from mathematical equations, leading to simpler calculations.

→ natural; → unit.

Uranium as found in nature. It contains 0.7% uranium-235, 99.3% uranium-238, and a trace of uranium-234 by weight.

→ natural; → uranium.

Philosophy: 1) The view of the world that takes account only of natural elements and forces, excluding the supernatural or spiritual.
2) The belief that all phenomena are covered by laws of science and that all teleological explanations are therefore without value (Dictionary.com).

→ natural; → -ism.

1) Of, pertaining to, or being above or beyond what is natural; unexplainable by natural; abnormal.
2) Of, pertaining to, characteristic of, or attributed to God or a deity (Dictionary.com).

→ super-; → natural.

Belief in the doctrine of supernatural or divine agency as manifested in the world, in human events, religious revelation, etc. (Dictionary.com).

→ super-; → naturalism.