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

The arrangement of parts in an object or organism.

M.E., from L. structura "a fitting together, adjustment, building," from structus, p.p. of struere "to pile, build, assemble," related to strues "heap," from PIE *stere- "to spread, extend, stretch out;" cf. Pers. gostar-, gostardan "to spread;" Av. star- "to spread," starati "spreads;" Skt. star- "to spread out, extend, strew," strnati "spreads;" Gk. stornumi "I spread out," strotos "spread, laid out;" Ger. Strahlung "radiation," from strahlen "to radiate," from Strahl "ray;" from M.H.G. strāle; from O.H.G. strāla "arrow, stripe."

Sâxtâr, from sâxt "made; make, construction, structure; style," past stem of sâxtan, sâzidan "to build, make, fashion; to adapt, adjust, be fit" (Mid.Pers. sâxtan, sâz-, Manichean Parthian s'c'dn "to prepare, to form;" Av. sak- "to understand, to mark," sâcaya- (causative) "to teach") + -âr verbal noun suffix.

The study of the processes that gave rise to the apparition of matter concentrations, such as → superclusters of galaxies, → galaxy clusters, and galaxies, in a homogeneous → expanding Universe. Cosmic structures are believed to result from → density fluctuations that existed in the → early Universe before radiation and matter decoupled (→ decoupling era or → recombination era). Initial → quantum fluctuations in the → inflaton field were expanded by → inflation. Inflation amplified them up to scales that correspond to those of galaxy clusters and beyond. Generally, a model of structure formation includes three main ingredients: 1) background cosmology, 2) model for fluctuation generation, and 3) types of → dark matter.
See also:
→ bottom-up structure formation, → hierarchical structure formation, → Silk damping, → top-down structure formation.

→ structure; → formation.

A cosmological model of → structure formation in which larger structures, such as galaxy → superclusters or perhaps even the vast → filaments and → voids, form earlier and then they fragment into smaller structures such as individual galaxies. Opposite of → bottom-up structure formation.

→ top; → down; → structure; → formation.

A type of → data structure in which each element is attached to one or more elements in a hierarchical manner. Trees are often called inverted trees because they are normally drawn with the root at the top.

→ tree; → structure.