Crucial - At a Crossroads

"If you ride to the left, you will lose your horse; if you ride to the right, you will lose your head."
A Knight at the Crossroads by Victor M. Vasnetsov (1848-1926)

CRUCIAL

Adjective. Early 18th century.

[French, from Latin cruc-, crux cross: see -IAL. In sense 2 from instantia crucis (Bacon) crucial instance.]

1 Chiefly ANATOMY. Of the form of a cross, cruciate. Now rare. E18

2(a) That finally decides between hypotheses;
relating of leading to decision between hypotheses;
decisive; critical;
colloquial. very important. M19

2(b) Excellent. slang. L20

Don't be cross: crucial is a word we're all probably guilty of misusing, steadily diluting its meaning from 'decisive, critical', to merely 'very important'. Its earliest use was in the sense of cross-shaped, primarily in anatomical descriptions such as cruciate ligaments. Its development into that which is decisive came from the logical term instantia crucis, meaning crucial instance, being an experiment so designed as to disprove all other hypotheses (though not necessarily proving the experimenter's hypothesis). Seemingly, this draws on the metaphor of standing at a crossroads, where one can go this way or that, and the outcome to that decision will, critically, be decisive.

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