An Etymological Dictionary of Astronomy and Astrophysics

1. Fundamentally → important; → principal.
   

2. → cardinal number.

Etymology (EN): M.E., from L.L. cardinalis “principal, pivotal,” lit. “serving as a hinge,” from cardo, cardin- “door hinge.”

Etymology (PE): Agrâ, from Av. aγra-, aγrya- “the highest, the first, foremost” cf. Skt. agra- “foremost, first, prominent,” PIE *agro- “top, first, beginning.”