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

A large on-line astronomical database, developed at the Centre de Données astronomiques de Strasbourg, → CDS in France. It provides a large collection of astronomical data, including cross-identifications, bibliography, and measurements for astronomical objects outside the solar system.

SIMBAD, short for Set of Identifications, Measurements, and Bibliography for Astronomical Data.

1) Geometry: Having the same shape; representing the same figure drawn to different scales (same corresponding angles and proportional sides).
2) Math.: Related by means of a → similarity transformation.

From Fr. similaire, from L. similis "like," → simulate.

Hamânand, contraction of hammânand, from ham-, → com-, + mânand "resembling, like," → simulate.

Two → square matrices A and B that are related by B = X^-1AX, where X is a square → nonsingular matrix.

→ similar; → matrix.

Polygons that are exactly the same shape, but can be different sizes.

→ similar; → polygon.

The state of being similar; likeness; resemblance.

→ similar; → -ity.

1) A transformation that preserves angles and changes all distances in the same ratio.
2) A transformation of the form B = X^-1AX relating two → square matrices A and B.

→ similarity; → transformation.

1) Chem.: Composed of only one → substance or → element.
2) Math.: Consisting of, involving, or describable by → terms of the → first degree.
3) Music: Uncompounded or without overtones.

M.E., from O.Fr. simple, from L. simplus "simple, single," variant of simplex, from PIE root *sem- "one, together;" cf. Pers. ham "together," → com-, Skt. sam "together;" + *plac- "-fold," from PIE *plek- "to plait," → multiply.

Sâdé "simple, unmixed, smooth, erased, plain;" cf. Khotanese sāta- "smooth;" Baluchi sāt/sāy-, sāh- "to shave;" Av. si-, sā- "to sharpen, cut;" Skt. śā- "to sharpen, whet" (Cheung 2007); see also → precise.

Statistics: An event consisting of a single point of the → sample space.

→ simple; → event.

A fraction in which the → numerator and → denominator are positive → integer numbers. Compare → compound fraction.

→ simple; → fraction.

The motion of a body subjected to a restraining force which is directly proportional to the displacement from a fixed point in the line of motion. The equation of simple harmonic motion is given by x = A sin(ωt + θ₀), where x is the body's displacement from equilibrium position, A is the → amplitude, or the magnitude of harmonic oscillations, ω is the → angular frequency, t is the time elapsed, and θ₀ is the → initial phase angle.

→ simple; → harmonic; → motion.

An oscillator whose force is proportional to its extension, according to → Hooke's law. The way the oscillator moves is called → simple harmonic motion.

→ simple; → harmonic; → oscillator.

A set of stars resulting from a spatially (≤ few pc) and temporally (≤ Myr) correlated star formation event.

→ simple; → population.

A → rootx₀ of function f(x), if f(x₀) = 0 and df/dx | x₀ = 0. See also → double root.

→ simple; → root.

A generalization of the simplest closed configuration that can be made from straight line segments. For example, a → triangle is a 2-simplex because it is in two → dimensions, and → tetrahedron is a 3-simplex because it is in three dimensions (Steven Schwartzman, An Etymological Dictionary of Mathematical Terms Used in English, 1994).

Simplex, literally "uncomplicated, → simple," from sim-, from PIE root *sem- "one, once, together" + plek- "to fold." "folded [only] once."

Taktâft, literally "folded once," from tak "→ single, alone," + tâft, contraction of tâfté "plated, twisted, fold," as in hamtâft, → complex.

An → algorithm for solving the classical → linear programming problem; developed by George B. Dantzig in 1947. The simplex method is an → iterative method, solving a system of → linear equations in each of its steps, and stopping when either the → optimum is reached, or the solution proves infeasible. The basic method remained pretty much the same over the years, though there were many refinements targeted at improving performance (e.g. using sparse matrix techniques), numerical accuracy and stability, as well as solving special classes of problems, such as mixed-integer programming (Free On-Line Dictionary of Computing, FOLDOC).

→ simplex; → method.

The act of simplifying, or the fact of being simplified.

Verbal noun of → simplify.

1) To make less complex or complicated.
2) Math.: Reduce an → expression by → algebraic manipulations.

→ simple + epenthesis -i- + → -fy.

Minute images or replicas of objects supposed by ancient atomist philosophers to be shed from any object and used in the explanation of vision. According to Democritus (c. 460-c. 370 BC) and Epicurus (341-270 BC), these replicas or effigies, called eidola, were perpetually peeled off the surfaces of things and caused vision by entering in the eye.

L. translation of eidola by Lucretius (1st Century BC), from L. simulacrum "likeness, image," from simulare "to → simulate."

To create a likeness or model of something (a situation, system, or the like).

M.E., from L. simulatus, p.p. of simulare "to imitate," from stem of similis "like;" cognate with Pers. ham "together, with; same, equally, even" (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- "one and the same," Skt. sama-, Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-).

Mânadidan verb from mânand "resembling, like," variant mânestan "to resemble;" Mid.Pers. mânag "like, resembling;" Av. man- "to resemble;" hamânad sâxtan, from hamânand, from ham-, as above, + mânad + sâxtan "to make, build."

The construction of a mathematical model to reproduce the characteristics of a phenomenon, system, or process, often using a computer, in order to infer information or solve problems.

Verbal noun of → simulate.