crux

Definition of Crux in English :

a small conspicuous constellation in the southern hemisphere in the Milky Way near Centaurus

the most important point

WordNet Lexical Database for English. Princeton University. 2010.

Crux

nounWord forms: plural cruxes or cruces (ˈkruːsiːz )

1.

a vital or decisive stage, point, etc (often in the phrase the crux of the matter)

2.

a baffling problem or difficulty

3. mountaineering

the most difficult and often decisive part of a climb or pitch

4. a rare word for cross

nounWord forms: Latin genitive Crucis (ˈkruːsɪs )

the more formal name for the Southern Cross

nounWord forms: plural ˈcruxes or ˈcruˌces (ˈkruˌsiz ; kro̅oˈsēzˌ)

1. Heraldry

a cross

2.

a difficult problem; puzzling thing

3.

the essential or deciding point

4. [C-]

a small S constellation near the celestial pole containing the Coalsack; the Southern Cross; the Cross

n. pl. crux·es or cru·ces (krsēz)

1. The basic, central, or critical point or feature: the crux of the matter; the crux of an argument.

2. A puzzling or apparently insoluble problem.

3. The most difficult portion of an ascent in rock climbing or mountaineering.

n.