cardinal

What it means

1. Of fundamental importance; crucial, pivotal.

   a cardinal rule

   3 more examples

   But cardinal sins, and hollow hearts, I fear ye.

   1613 (date written), William Shakespeare, [John Fletcher], “The Famous History of the Life of King Henry the Eight”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, (please specify the act number in uppercase Roman numerals, and the scene number in lowercase Roman numerals)

   the cardinal intersections of the zodiack

   1650, Thomas Browne, Pseudodoxia Epidemica: […], 2nd edition, London: […] A[braham] Miller, for Edw[ard] Dod and Nath[aniel] Ekins, […], →OCLC

   Impudence is now a cardinal virtue.

   a. 1631, Michael Drayton, To my noble friend Mr. William Brown, of the evil time

2. nauticalOf or relating to the cardinal directions (north, south, east and west).

   a cardinal mark

3. Describing a “natural” number used to indicate quantity (e.g., zero, one, two, three), as opposed to an ordinal number indicating relative position.

In a sentence

a cardinal rule

Where it comes from

1. Latincardō
2. Proto-Indo-European*h₂el-
3. Proto-Indo-European*h₂élisder.?
4. Latincardinālis
5. Middle Frenchcardina
6. Englishcardinal

From Middle French cardinal, from Latin cardinālis (“pertaining to a hinge, hence applied to that on which something turns or depends, important, principal, chief”), from cardin-, cardō (“hinge”) + -ālis, adjectival suffix.