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

(adj.): Existing or having its specific nature only by relation to something else; not absolute or independent.
See also: → relative atomic mass, → relative azimuth, → relative dating, → relative density, → relative error, → relative frequency, → relative humidity, → relative invariant, → relative tensor, → relative vector, → relative permeability, → relative refractive index, → relative sunspot number, → relative velocity, → relatively, → relativity.

From M.E. relatif (n.), from O.Fr. relatif, from L.L. relativus "having reference or relation," from L. relatus, suppletive p.p. of referre "to refer," → relate.

Bâzâni, from bâzân- present stem of bâzânidan, → relate, + -i adj. suffix.

The ratio of the mass of an atom of the → chemical element to one-twelfth the mass of an atom of carbon-12. Because an element in nature is usually a mixture of isotopes, the relative atomic mass is also the weighted mean of the atomic masses of all the atoms in a particular sample of the element, weighted by isotopic abundance. In this sense, relative atomic mass was once known as → atomic weight.

→ relative; → atomic; → mass.

The difference in → azimuth between the → Moon and the → Sun.

→ relative; → azimuth.

A method of dating that can only tell us whether an event or object is older or younger than another event or object. In geology, different layers of rock are compared to determine an ordered sequence of events in geologic history. In contrast to → absolute dating, relative dating cannot give the actual age of a rock. See also → stratigraphy.

→ relative; → dating.

The ratio of the density of a substance to the density of a given reference material. For a solid or liquid, it is the density (at 20°C) relative to the maximum density of water (at 4°C). For a gas is its density divided by the density of hydrogen (or sometimes dry air) at the same temperature and pressure. Also called → specific density.

→ relative; → density.

The → absolute error divided by the true value x, that is: Δx/x. The result may be expressed as a percentile and is useful when we want to determine the error relative to the value of the exact quantity.

→ relative; → error.

Statistics: The number of the occurrences of an event divided by the number of observations.

→ relative; → frequency.

The amount of moisture in the air compared to what the air can "hold" at that temperature. It is given by the ratio of the partial pressure of water vapor in the mixture to the saturated vapor pressure of water at a specific temperature.

→ relative; → humidity.

A → relative tensor of order zero.

→ relative; → invariant.

→ magnetic permeability.

→ relative; → permeability.

The ratio of the sine of the angle of incidence to the sine of the angle of refraction for a ray passing out of one of the media into the other.

→ relative; → refractive; → index.

Same as → Wolf number and → sunspot number.

→ relative; → sunspot; → number.

A generalized tensor concept that is characterized by a → Jacobian matrix of transformation raised to a power called → weight of a tensor density. In practice, only relative tensors of weight 1 or -1 are used. The product of a relative tensor of weight -1 by another tensor of weight 1 is an → absolute tensor. Same as → tensor density.

→ relative; → tensor.

A → relative tensor of → order  → one.

→ relative; → vector.

For two objects A and B, the velocity which B, supposing itself at rest, assigns to A.

→ relative; → velocity.

In a relative manner; in relation to something else.

From → relative + -ly "-vâr, -âné."