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

1) Fundamentally → important; → principal.
2) → cardinal number.

M.E., from L.L. cardinalis "principal, pivotal," lit. "serving as a hinge," from cardo, cardin- "door hinge."

Agrâ, from Av. aγra-, aγrya- "the highest, the first, foremost" cf. Skt. agra- "foremost, first, prominent," PIE *agro- "top, first, beginning."

Any of the four principal directions or points of the compass, → north, → east, → south, and → west. See also: → cardinal point.

→ cardinal; → direction.

An ordinary number such as 0, 1, 2, or 3, as opposed to an → ordinal number such as 1st, 2nd, or 3rd. Cardinal numbers can be → zero or → positive and are used for counting the things that are assumed to be not divisible.

→ cardinal; → number.

One of the four points where the → meridian and the → prime vertical intersect the → horizon. See also: → cardinal direction.

→ cardinal; → point.

Math.: The → cardinal number indicating the → number of → elements in a → set. For example, the set A = {a, b, c, d} contains 4 elements, and therefore it has a cardinality of 4 (denoted |A| = 4).

→ cardinal; → -ity.